Voltage-dependent resistor and method of making the same

Abstract

The present invention provides a voltage-dependent resistor of the bulk-type in which zinc oxide (ZnO) powder and additives are admixed to form a sintered body composition having as the main constituent, zinc oxide, and in which the mixture is formed into a resistor body, the body is sintered, and electrodes are applied to the opposite surfaces of the sintered body, the improvement comprising the step of, prior to sintering and admixture with said zinc oxide, admixing all amount of boron oxide (B.sub.2 O.sub.3) with other additives in the form of a borosilicate glass, which is composed of 5 to 30 weight percent of boron oxide (B.sub.2 O.sub.3) and 70 to 95 weight percent of silicon oxide (SiO.sub.2). A process for the production of said resistor is also provided.

Description

This invention relates to a voltage-dependent resistor (varistor) having non-ohmic properties (voltage-dependent property) due to the bulk thereof and a process for making it. This invention relates more particularly to a voltage-dependent resistor, which is suitable for a lightning arrester and a surge absorber.

Various voltage-dependent resistors have been widely used for suppression of abnormally high surges induced in electrical circuits. The electrical characteristics of such voltage-dependent resistors are expressed by the relation:

I=(V/C).sup.n ( 1) where V is the voltage across the resistor, I is the current flowing through the resistor, C is a constant corresponding to the voltage at a given current and exponent n is a numerical value greater than 1. The value of n is calculated by the following equation: ##EQU1## where V.sub.1 and V.sub.2 are the voltage at given currents I.sub.1 and I.sub.2, respectively. Usually I.sub.1 is 0.1 mA and I.sub.2 is 1 mA. The desired volue of C depends upon the kind of application to which the resistor is to be put. Usually C value is expressed by the voltage at 1 mA per mm. It is ordinarily desirable that the value of C is between several scores of volts and several hundreds volts. The value of n is desired to be as large as possible because this exponent determines the extent to which the resistors depart from ohmic characteristics. Conveniently, n-value defined by I.sub.1, I.sub.2, V.sub.1 and V.sub.2 as shown in equation (2) is expressed by .sub.1 n.sub.2 for distinguishing from n-value calculated by other currents or voltages. For application to a surge absorber and a lightning arrester, it is desirable that the residual (clamp) voltage ratio (which is expressed by the ratio of the voltage at xA (V.sub.xA) and the voltage at 1 mA (V.sub.1 mA); V.sub.xA /V.sub.1 mA) be small since this ratio determines the ability to protect the equipment and components in electrical circuits against surges. Usually x is 100, so the residual voltage ratio is evaluated by V.sub.100 A /V.sub.1 mA. It is also desirable that the change rate of C-value after impulse application be as close to zero as possible. This characteristic is called surge withstand capability and is usually expressed by the change rate of C value after two applications of impulse current of 1000 A whose wave form is 8.times.20 .mu.s.

As voltage-dependent resistors for a lightning arrester, silicon carbide varistors and zinc oxide voltage-dependent resistors are known. The silicon carbide varistors have nonlinearity due to the contacts among the individual grains of silicon carbide bonded together by a ceramic binding material, i.e. to the bulk, and the C-value is controlled by changing a dimension in the direction in which the current flows through the varistors. In addition, the silicon carbide varistors have good surge withstand capability thus rendering them suitable e.g. as surge absorbers and as characteristic elements of lightning arresters. The characteristic elements are used usually by connecting them in series with discharging gaps and determine the level of the discharging voltage and the follow current.

However, the silicon carbide varistors have a relatively low n-value ranging from 3 to 7 which results in a poor suppression of lightning surge or increase in the follow current. Another defect of the arrester with a discharging gap is slow response to surge voltage and a very short rise time such as below 1 .mu.s. It is desirable for the arrester to suppress the lightning surge and the follow current to a level as low as possible and respond to surge voltage instantaneously. The silicon carbide varistors, however, have a relatively low n-value ranging from 3 to 7 which results in poor surge suppression.

There have been known, on the other hand, voltage-dependent resistors of the bulk type comprising a sintered body of zinc oxide with additives, as seen in U.S. Pat. Nos. 3,633,458, 3,632,529, 3,634,337, 3,598,763, 3,682,841, 3,642,664, 3,648,725, 3,687,871, 3,723,175, 3,778,743, 3,806,765, 3,811,103, 3,936,396, 3,863,193, 3,872,582 and 3,953,373. These zinc oxide voltage-dependent resistors of the bulk type contain, as additives, one or more combinations of oxides of fluorides of bismuth, cobalt, manganese, barium, boron, berylium, magnesium, calcium, strontium, titanium, antimony, germanium, chromium and nickel, and the C-value is controllable by changing, mainly, the compositions of said sintered body and the distance between electrodes and they have excellent voltage-dependent properties in n-value.

Conventional zinc oxide voltage-dependent resistors have such a large n-value that they were expected to be used without series discharging gaps as characteristic elements in lightning arresters. However, zinc oxide voltage-dependent resistors still have a big problem to be solved in order to be applied to lightning arresters without series discharging gaps. The problem is the thermal run away life under continuous voltage stress, especially with application of surges. This is one of the most important problems to be solved in practice. When a zinc oxide voltage-dependent resistor is applied to the lightning arrester without a series discharging gap, the voltage of the circuit or the distribution line is designed to be in the range from 50 to 80 percent of the varistor voltage (the voltage between electrodes at 1 mA) of the zinc oxide voltage-dependent resistor. Accordingly, the total varistor voltage of zinc oxide voltage-dependent resistors which is connected in series is designed to be in the range from 120 kV to 75 kV for the application to the lightning arrestor in a 60 kV electric power transmission line.

In Japan, they usually have 10 to 30 thunderstorm days a year, though it depends on the district. On those days, the lightning arresters are subjected to lightning surges. If the number of lightning surges are assumed to be about 10 per thunderstorm day, the lightning arresters must be subjected to 100 to 300 lightning surges a year. The lightning arresters are usually used for more than 20 years, so that they must withstand at least 2000 to 6000 lightning surges with the voltage stress of 60 kV for 20 years. The average impulse current flowing through the zinc oxide voltage-dependent resistors in the lightning arresters is about 100 A (in the waveform of 8.times.20 .mu.s). Accordingly, the zinc oxide voltage-dependent resistor in the lightning arresters without series discharging gaps must have thermal run away life of more than 20 years under the continuous voltage stress of 60 kV with 2000 to 6000 lightning surges of 100 A of the waveform of 8.times.20 .mu.s.

Conventional zinc oxide voltage-dependent resistors show fairly good surge withstand capability and stability for the change of environment in a separate condition. That is, they show a fairly good surge withstand capability without continuous voltage stress at the same time or they show a fairly good stability against voltage stress for a long term without the shooting of impulse currents at the same time. However, the conventional zinc oxide voltage-dependent resistors do not show a sufficient thermal run away life over a long term under a condition where they have both a voltage stress of 80 to 50 percent of the varistor voltage and 2000 to 6000 surges of impulse currents of 100 A at the same time. The development of the voltage-dependent resistors having an enough thermal run away life under continuous voltage stress with surges has been required for the application to lightning arresters without series discharging gaps.

An object of the present invention is to provide a voltage-dependent resistor, and a method for making it, having a high n-value, a low residual voltage ratio, a good surge withstand capability and a long thermal run away life under continuous voltage stress with surges. The characteristics of high n-value, low residual voltage ratio and good surge withstand capability is indispensable for the application of lightning arresters. The last one, the long thermal run away life under continuous voltage stress with surges, is one of the most important characteristics which should be improved for that application.

This and other objects and features of this invention will become apparent upon consideration of the following detailed description taken together with the accompanying drawing is which the single FIGURE in a cross-sectional view of a voltage-dependent resistor in accordance with this invention.

Before proceeding with a detailed description of the manufacturing process of the voltage-dependent resistor contemplated by this invention, its construction will be described with reference to the single FIGURE, wherein reference numeral 10 designates, as whole, a voltage-dependent resistor comprising, as its active element, a sintered body having a pair of electrodes 2 and 3 in an ohmic contact with two opposite surfaces thereof. The sintered body 1 is prepared in a manner hereinafter set forth and is in any form such as circular, square of rectangular plate form. This invention also provides a process for making a bulk-type voltage-dependent resistor comprising a sintered body consisting essentially of, as a major part, zinc oxide (ZnO), and additives, and having electrodes to the opposite surfaces of said sintered body, characterized by a high n-value, a low residual voltage ratio, a good surge withstand capability and especially a long thermal run away life under continuous voltage stress with surges.

It has been discovered according to the invention that a voltage-dependent resistor comprising a sintered body of a composition which comprises, as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), at least one member selected from the group consisting of 0.1 to 10 mole percent of silicon oxide (SiO.sub.2) and 0.1 to 3 mole percent of nickel oxide (NiO), at least one member selected from the group consisting of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and if necessary, 0.00005 to 0.3 mole percent of silver oxide (Ag.sub.2 O), and the remainder being zinc oxide (ZnO) as a main constituent, with electrodes applied to opposite surfaces of the sintered body, has a non-ohmic property (voltage-dependent property) due to the bulk itself. Therefore, its C-value can be changed without impairing its n-value by changing the distance between the electrodes at opposite surfaces.

According to this invention, a voltage-dependent resistor has a high n-value, a small residual voltage ratio, a good surge withstand capability and a long thermal run away life under continuous voltage stress with surges. According to this invention, the n-value and the thermal run away life under continuous voltage stress with surges are improved by adding as additives the entire amount of boron oxide and silver oxide and a part of the cobalt oxide and silicon oxide in glass frit form.

EXAMPLE 1-1

Zinc oxide and additives as shown in Tables 1 and 2 were mixed in a wet will for 24 hours. Each of the mixtures was dried and pressed in a mold disc of 17.5 mm in diameter and 2 mm in thickness at a pressure of 250 kg/cm.sup.2. The pressed bodies were sintered in air at 1230.degree. C. for 2 hours, and then furnace-cooled to room temperature. Each sintered body was lapped at the opposite surfaces thereof into the thickness of 1.5 mm by silicon carbide abrasive in particle size of 30 .mu.m in mean diameter. The opposite surfaces of the sintered body were provided with spray metallized films of aluminum by a per se well known technique.

The electrical characteristics of the resultant sintered bodies are shown in Tables 1 and 2, which show that C-values of unit thickness (1 mm), n-values defined between 0.1 mA and 1 mA according to the equation (2), residual voltage ratios of V.sub.100 A to V.sub.1 mA, change rates of C-values after the impulse test and thermal run away lives under continuous voltage stress with surges.

The voltage at 100 A (V.sub.100 A) is measured by using a waveform expressed by 8.times.20 .mu.s. The change rate against surge is evaluated measuring the change rate of C-value of the voltage-dependent resistor after applying 2 impulse currents of 1000 A whose waveform is expressed by 8.times.20 .mu.s. The thermal run away life was evaluated by the time until a thermal run away occurs under conditions such that both the AC voltage (60 Hz) whose amplitude is 80 percent of C-value and the impulse current of 100 A, 8.times.20 .mu.s are applied at the same time at a constant temperature of 100.degree. C.

Tables 3 and 4 show that an n-value above 40, a residual voltage ratio velow 1.60, a surge withstand capability below -5.0 percent, a thermal run away life under voltage stress with surges more than 50 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2).

EXAMPLE 1-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 3 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 4 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 4 shows an improvement of n-value of the more than 10 and an improvement in the thermal run away life of more than 20 hours.

Table 4 shows that the n-value is improved from above 40 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 50 to more than 70 by adding as an additive, the entire amount of boron oxide (B.sub.2 O.sub.3) in the form of borosilicate glass.

EXAMPLE 1-3

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 5 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 6 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 6 shows an improvement of the n-value of more than 20 and an improvement in the thermal run away life of more than 30 hours.

Table 6 shows that the thermal run away life under voltage stress with surges is improved from more than 50 to more than 80 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3) and a part of bismuth oxide (Bi.sub.2 O.sub.3) in the form of borosilicate bismuth glass.

EXAMPLE 1-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 7 were fabricated into voltage deendent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 8 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 8 shows an improvement of the n-value of more than 20 and an improvement in the thermal run away life of more than 30 hours.

Table 8 shows that the n-value is improved from above 40 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 50 to more than 80 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), a part of bismuth oxide (Bi.sub.2 O.sub.3) and a part of cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate bismuth glass with cobalt oxide.

EXAMPLE 2-1

Zinc oxide and additives of Table 9 and 10 were fabricated into voltage-dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Tables 9 and 10 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges are shown.

Tables 9 and 10 show that an n-value above 50, a residual voltage ratio below 1.60, a surge withstand capability below -5.0 percent, a thermal run away life under voltage stress with surges of more than 100 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2) and 0.0005 to 0.3 mole percent of silver oxide (Ag.sub.2 O).

EXAMPLE 2-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 11 were fabricted into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 12 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 12 shows an improvement of n-value of the more than 10 and an improvement in the thermal run away life of more than 20 hours.

Table 12 shows that the n-value is improved from above 50 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 120 by adding the additives of all amount of boron oxide (B.sub.2 O.sub.3) and all amount of silver oxide (Ag.sub.2 O), in the form of borosilicate glass with silver oxide.

EXAMPLE 2-3

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 13 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 14 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 14 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life of more than 30 hours.

Table 14 shows that the n-value is improved from above 50 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 130 by adding as additives the entire amount of boron oxide (B.sub.2 O.sub.3), the entire amount of silver oxide (Ag.sub.2 O) and a part of bismuth oxide (Bi.sub.2 O.sub.3) in the form of borosilicate bismuth glass.

EXAMPLE 2-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 1 and 2 and glass frits whose composition is shown in Table 15 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 16 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 16 shows an improvement of the n-value of more than 20 and an improvement in the thermal run away life of more than 30 hours.

Table 16 shows that the n-value is improved from above 50 to above 70 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 130 by adding as additives the entire amount of boron oxide (B.sub.2 O.sub.3), the entire amount of silver oxide (Ag.sub.2 O), a part of the bismuth oxide (Bi.sub.2 O.sub.3) and a part of the cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate bismuth glass with silver oxide and cobalt oxide.

EXAMPLE 3-1

Zinc oxide and additives of Table 17 and 18 were fabricated into voltage-dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Tables 17 and 18 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges are shown.

Tables 17 and 18 show that an n-value above 30, a residual voltage ratio below 1.70, a surge withstand capability below -4.0 percent, a thermal run away life under voltage stress with surges, of more than 50 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and 0.1 to 3.0 mole percent of nickel oxide (NiO).

EXAMPLE 3-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 17 and 18 and glass frits whose composition is shown in Table 3 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 19 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 19 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life of more than 20 hours.

Table 19 shows that the n-value is improved from above 30 to above 40 and the thermal run away life under voltage stress with surges is improved from more than 50 to more than 70 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), in the form of borosilicate glass.

EXAMPLE 3-3

Zinc oxide and additives of No. a-1 or No. b-1 in Table 17 and 18 and glass frits whose composition is shown in Table 5 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 20 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 20 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life of more than 30 hours.

Table 20 shows that the n-value is improved from above 30 to above 40 and the thermal run away life under voltage stress with surges is improved from more than 50 to more than 80 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), and a part of the bismuth oxide (Bi.sub.2 O.sub.3) in the form of borosilicate bismuth glass.

EXAMPLE 3-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 17 and 18 and glass frits whose composition is shown in Table 9 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 21 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 21 shows an improvement of the n-value more than 20 and the improvement in the thermal run away life of more than 30 hours.

Table 21 shows that the n-value is improved from above 30 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 50 to more than 80 hours by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), the entire amount of silver oxide (Ag.sub.2 O), a part of the bismuth oxide (Bi.sub.2 O.sub.3) and a part of the cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate bismuth glass with cobalt oxide.

EXAMPLE 4-1

Zinc oxide and additives of Table 22 and 23 were fabricated into voltage-dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Tables 22 and 23 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges are shown.

Tables 22 and 23 show that an n-value above 40, a residual voltage ratio below 1.70, a surge withstand capability below -4.0 percent, a thermal run away life under voltage stress with surges more than 100 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.0005 to 0.3 mole percent of silver oxide (Ag.sub.2 O).

EXAMPLE 4-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 17 and 18 and glass frits whose composition is shown in Table 11 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 24 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 24 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life more than 20 hours.

It has been discovered according to the present invention that the n-value is improved from above 40 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 120 hours by adding an additives, the entire amount of boron oxide (B.sub.2 O.sub.3) and the entire amount of silver oxide (Ag.sub.2 O) in the form of borosilicate glass with silver oxide.

EXAMPLE 4-3

Zinc oxide and additives of No. 17 or No. 18 in Table 17 and 18 and glass frits whose composition is shown in Table 13 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 25 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 25 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life of more than 30 hours.

Table 25 shows that the n-value is improved from above 40 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 130 by adding the additives of the entire amount of boron oxide (B.sub.2 O.sub.3), all amount of the silver oxide (Ag.sub.2 O), and a part of bismuth oxide (Bi.sub.2 O.sub.3) in the form of borosilicate bismuth glass with silver oxide.

EXAMPLE 4-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 17 and 18 and glass frits whose composition is shown in Table 15 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 26 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 26 shows an improvement of n-value of the more than 20 and an improvement in the thermal run away life more than 30 hours.

Table 26 shows that the n-value is improved from above 40 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 100 to more than 130 hours by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), the entire amount of silver oxide (Ag.sub.2 O), a part of the bismuth oxide (BiO.sub.3) and a part of cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate glass with silver oxide and cobalt oxide.

EXAMPLE 5-1

Zinc oxide and additives of Table 27 and 28 were fabricated into voltage-dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Tables 27 and 28 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges are shown.

Tables 27 and 28 show that an n-value above 40, a residual voltage ratio below 1.60, a surge withstand capability below -3.0 percent, a thermal run away life under voltage stress with surges more than 150 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and both of 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2).

EXAMPLE 5-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 3 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 29 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 29 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away life of more than 10 hour.

Table 29 shows that the n-value is improved from above 40 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 150 to more than 160 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), and a part of the silicon oxide (SiO.sub.2) in the form of borosilicate glass.

EXAMPLE 5-3

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 5 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 30 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 30 shows improvement of n-value of more than 10 and an improvement in the thermal run away life of more than 20 hours.

Table 30 shows that the n-value is improved from above 40 to above 50 and the thermal run away life under voltage stress with surges is improved from more than 150 to more than 170 hours by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), and a part of the bismuth oxide (Bi.sub.2 O.sub.3) in the form of the borosilicate bismuth glass.

EXAMPLE 5-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 7 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 31 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 31 shows that the improvement of n-value of more than 20 and the improvement of the thermal run away life more than 20 hours.

Table 31 shows that the n-value is improved from above 40 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 150 to more than 170 by adding the additives of all amount of boron oxide (B.sub.2 O.sub.3), a part of bismuth oxide (Bi.sub.2 O.sub.3) and a part of cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate bismuth glass with cobalt oxide.

EXAMPLE 6-1

Zinc oxide and additives of Table 32 and 33 were fabricated into voltage-dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Tables 32 and 33 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges are shown.

Tables 32 and 33 show that an n-value above 50, a residual voltage ratio below 1.60, a surge withstand capability below -3.0 percent, a thermal run away life under voltage stress with surges for more than 190 hours can be obtained when said sintered body comprises, as a main constituent, zinc oxide (ZnO), and as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), and at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and both 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2) and 0.0005 to 0.3 mole percent of silver oxide (Ag.sub.2 O).

EXAMPLE 6-2

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 15 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 34 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 34 shows an improvement of n-value of more than 10 and an improvement in the thermal run away life more than 20 hours.

Table 34 shows that the n-value is improved from above 50 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 190 to more than 210 hours by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3) and the entire amount of the silver oxide (Ag.sub.2 O) in the form of borosilicate glass with silver oxide.

EXAMPLE 6-3

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 13 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 35 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 35 shows an improvement of the n-value of more than 10 and an improvement in the thermal run away of life more than 30 hours.

Table 35 shows that the n-value is improved from above 50 to above 60 and the thermal run away life under voltage stress with surges is improved from more than 190 to more than 220 by adding as additives, the entire amount of the boron oxide (B.sub.2 O.sub.3), the entire amount of the silver oxide (Ag.sub.2 O) and a part of the bismuth oxide (Bi.sub.2 O.sub.3) in the form of borosilicate bismuth glass with silver oxide.

EXAMPLE 6-4

Zinc oxide and additives of No. a-1 or No. b-1 in Table 27 and 28 and glass frits whose composition is shown in Table 19 were fabricated into voltage dependent resistors by the same process as that of Example 1-1. The electrical properties of the resultant resistors are shown in Table 36 in which the C-values of unit thickness (1 mm), the n-values defined between 0.1 mA and 1 mA, and the residual voltage ratios of V.sub.100 A to V.sub.1 mA, the change rates of C-value after impulse test and the thermal run away lives under continuous voltage stress with surges. Table 36 shows an improvement of n-value of more than 20 and an improvement in the thermal run away life more than 30 hours.

Table 36 shows that the n-value is improved from above 50 to above 70 and the thermal run away life under voltage stress with surges is improved from more than 190 to more than 220 by adding as additives, the entire amount of boron oxide (B.sub.2 O.sub.3), all amount of the silver oxide (Ag.sub.2 O), a part of bismuth oxide (Bi.sub.2 O.sub.3) and a part of cobalt oxide (Co.sub.2 O.sub.3) in the form of borosilicate bismuth glass with silver oxide and cobalt oxide.

TABLE 1__________________________________________________________________________ Change rate Thermal after run Impulse awayAdditives (mole %) C-Value test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) n-Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________a-1 0.5 0.5 0.5 1.0 0.5 0.5 0.0025 0 212 50 1.47 -5.2 9a-2 " " " " " " " 0.005 211 53 1.45 -3.9 52a-3 " " " " " " " 0.3 211 55 1.46 -4.5 58a-4 " " " " " " 0 0.1 211 54 1.71 -6.5 7a-5 " " " " " " 0.0005 " 210 53 1.47 -2.9 53a-6 " " " " " " 0.025 " 221 45 1.53 -2.9 55a-7 " " " " " 0 0.0025 " 149 51 1.53 -5.3 43a-8 " " " " " 0.1 " " 175 59 1.49 -4.5 53a-9 " " " " " 10.0 " " 433 59 1.45 -2.8 55a-10 " " " " 0 0.5 " " 185 52 1.54 -6.1 47a-11 " " " " 0.05 " " " 190 53 1.52 -3.5 53a-12 " " " " 1.5 " " " 232 45 1.56 -4.4 53a-13 " " " 0 0.5 " " " 174 42 1.53 -6.5 45a-14 " " " 0.1 " " " " 188 51 1.48 -3.5 52a-15 " " " 3.0 " " " " 251 55 1.49 -3.4 54a-16 " " 0 1.0 " " " " 149 27 1.73 -6.3 51a-17 " " 0.1 " " " " " 202 50 1.52 -4.1 41a-18 " " 3.0 " " " " " 210 48 1.53 -4.0 52a-19 " 0 0.5 " " " " " 132 29 1.73 -6.5 42a-20 " 0.1 " " " " " " 178 43 1.56 -3.8 51a-21 " 3.0 " " " " " " 221 56 1.56 -3.9 53a-22 0 0.5 " " " " " " 96 6 3.60 -6.5 35a-23 0.1 " " " " " " " 175 43 1.51 -3.8 52a-24 1.0 " " " " " " " 205 59 1.51 -4.2 56a-25 3.0 " " " " " " " 204 58 1.52 -4.3 58a-26 0.5 " " " " " " " 210 53 1.50 -4.5 57__________________________________________________________________________ TABLE 2__________________________________________________________________________ Change rate Thermal after run Impulse awayAdditives (mole %) C-Value test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) n-Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________b-1 0.5 0.5 0.5 1.0 0.5 0.5 0.0025 0 211 51 1.47 -5.3 8b-2 " " " " " " " 0.005 211 53 1.47 -4.0 53b-3 " " " " " " " 0.3 210 54 1.47 -4.6 58b-4 " " " " " " 0 0.1 212 54 1.70 -6.7 8b-5 " " " " " " 0.0005 " 210 53 1.47 -3.3 53b-6 " " " " " " 0.025 " 222 43 1.52 -3.3 56b-7 " " " " " 0 0.0025 " 150 51 1.52 -5.5 44b-8 " " " " " 0.1 " " 173 58 1.49 -4.6 53b-9 " " " " " 10.0 " " 431 58 1.44 -2.9 53b-10 " " " " 0 0.5 " " 183 51 1.53 -6.1 48b-11 " " " " 0.05 " " " 191 52 1.52 -3.7 52b-12 " " " " 1.5 " " " 230 44 1.55 -4.4 52b-13 " " " 0 0.5 " " " 173 42 1.53 -6.3 44b-14 " " " 0.1 " " " " 189 50 1.48 -3.5 51b-15 " " " 3.0 " " " " 252 53 1.48 -3.5 53b-16 " " 0 1.0 " " " " 150 25 1.72 -6.3 41b-17 " " 0.1 " " " " " 201 49 1.51 -4.1 50b-18 " " 3.0 " " " " " 210 47 1.53 -4.1 50b-19 " 0 0.5 " " " " " 131 26 1.73 -6.5 41b-20 " 0.1 " " " " " " 178 41 1.56 -3.8 50b-21 " 3.0 " " " " " " 219 53 1.56 -3.7 50b-22 0 0.5 " " " " " " 97 6 3.55 -6.0 37b-23 0.1 " " " " " " " 173 43 1.51 -3.8 51b-24 1.0 " " " " " " " 206 57 1.51 -4.1 56b-25 3.0 " " " " " " " 203 57 1.52 -4.5 57b-26 0.5 " " " " " " " 212 54 1.50 -4.7 55__________________________________________________________________________ TABLE 3______________________________________Glass composition No. B.sub.2 O.sub.3 SiO.sub.2______________________________________A1 5 95A2 15 85A3 30 70 (Wt. %)______________________________________ TABLE 4______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 A1 233 63 146 -4.2 77 A2 226 63 1.46 -4.1 77 A3 221 64 1.46 -3.8 78b-1 A1 235 64 1.46 -4.1 77 A2 227 64 1.46 -4.1 77 A3 220 64 1.46 -4.0 78______________________________________ TABLE 5______________________________________Glass Composition B.sub.2 O.sub.3 SiO.sub.2 Bi.sub.2 O.sub.3______________________________________B1 5 5 90B2 20 10 70B3 30 30 40 (Wt. %)______________________________________ TABLE 6______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 B1 211 64 1.46 -4.1 88 B2 212 64 1.46 -3.8 88 B3 213 63 1.46 -3.6 88b-1 B1 210 64 1.47 -4.1 87 B2 211 64 1.46 -3.9 88 B3 213 64 1.46 -3.8 88______________________________________ TABLE 7______________________________________Glass Composition No. B.sub.2 O.sub.3 SiO.sub.2 Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3______________________________________E1 5 8 85 2E2 10 5 75 10E3 10 15 70 5E4 25 25 40 10 (Wt. %)______________________________________ TABLE 8______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 E1 211 75 1.46 -3.7 88 E2 211 73 1.46 -3.7 88 E3 211 74 1.47 -3.6 89 E4 213 74 1.46 -3.6 89b-1 E1 211 74 1.47 -3.8 88 E2 211 74 1.47 -3.7 88 E3 212 74 1.47 -3.7 89 E4 213 74 1.47 -3.8 88______________________________________ TABLE 9__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- V.sub.100A / test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O.sub.3 (V/mm) Value V.sub.1mA (%) (hr)__________________________________________________________________________c-1 0.5 0.5 0.5 1.0 0.5 0.5 0.0025 0.1 0 210 53 1.50 -4.5 57c-2 " " " " " " " " 0.0005 211 58 1.48 -4.3 103c-3 " " " " " " " " 0.1 211 63 1.49 -4.4 105c-4 " " " " " " " " 0.3 213 65 1.48 -4.7 107c-5 " " " " " " " 0 0.1 211 55 1.47 -5.2 19c-6 " " " " " " " 0.005 " 211 58 1.45 -4.0 102c-7 " " " " " " " 0.3 " 211 59 1.45 -4.4 107c-8 " " " " " " 0 0.1 " 210 58 1.73 -6.6 18c-9 " " " " " " 0.0005 " " 210 55 1.45 -3.0 100c-10 " " " " " " 0.025 " " 222 51 1.53 -3.0 105c-11 " " " " " 0 0.0025 " " 150 53 1.53 -5.2 53c-12 " " " " " 0.1 " " " 177 62 1.45 -4.5 104c-13 " " " " " 10.0 " " " 440 62 1.46 -2.9 106c-14 " " " " 0 0.5 " " " 183 55 1.54 -5.8 49c-15 " " " " 0.05 " " " " 191 55 1.54 -3.5 102c-16 " " " " 1.5 " " " " 233 50 1.57 -4.3 103c-17 " " " 0 0.5 " " " " 170 51 1.54 -6.4 49c-18 " " " 0.1 " " " " " 185 56 1.49 -3.3 103c-19 " " " 3.0 " " " " " 252 59 1.49 -3.3 105c-20 " " 0 1.0 " " " " " 151 29 1.72 -6.7 39c-21 " " 0.1 " " " " " " 205 53 1.52 -4.0 100c-22 " " 3.0 " " " " " " 213 54 151 -4.0 101c-23 " 0 0.5 " " " " " " 135 28 1.74 -6.3 45c-24 " 0.1 " " " " " " " 181 51 1.55 -3.9 103c-25 " 3.0 " " " " " " " 221 59 1.55 -3.8 103c-26 0 0.5 " " " " " " " 99 6 3.55 -6.4 43c-27 0.1 " " " " " " " " 174 50 1.53 -3.8 103c-28 1.0 " " " " " " " " 204 63 1.53 -4.0 107c-29 3.0 " " " " " " " " 205 62 1.53 -4.1 109c-30 0.5 " " " " " " " " 211 55 1.51 -4.7 106__________________________________________________________________________ TABLE 10__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- V.sub.100A / test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O.sub.3 (V/mm) Value V.sub.1mA (%) (hr)__________________________________________________________________________d-1 0.5 0.5 0.5 1.0 0.5 0.5 0.0025 0.1 0 212 54 1.50 -4.7 55d-2 " " " " " " " " 0.0005 211 58 1.49 -4.3 104d-3 " " " " " " " " 0.1 211 62 1.49 -4.4 106d-4 " " " " " " " " 0.3 211 64 1.49 -4.6 108d-5 " " " " " " " 0 0.1 211 53 1.48 -5.3 19d-6 " " " " " " " 0.005 " 210 57 1.46 -4.1 101d-7 " " " " " " " 0.3 " 210 57 1.46 -4.4 106d-8 " " " " " " 0 0.1 " 210 57 1.73 -6.5 21d-9 " " " " " " 0.0005 " " 211 54 1.48 -3.3 101d-10 " " " " " " 0.025 " " 224 51 1.53 -3.0 106d-11 " " " " " 0 0.0025 " " 153 53 1.52 -5.5 51d-12 " " " " " 0.1 " " " 181 60 1.48 -4.3 105d-13 " " " " " 10.0 " " " 437 61 1.47 -3.1 108d-14 " " " " 0 0.5 " " " 182 54 1.55 -6.2 47d-15 " " " " 0.05 " " " " 180 55 1.55 -3.9 102d-16 " " " " 1.5 " " " " 225 51 1.57 -4.8 104d-17 " " " 0 0.5 " " " " 172 51 1.54 -6.5 47d-18 " " " 0.1 " " " " " 186 57 1.50 -3.3 103d-19 " " " 3.0 " " " " " 253 59 1.50 -3.4 106d-20 " " 0 1.0 " " " " " 150 27 1.73 -6.8 38d-21 " " 0.1 " " " " " " 205 52 1.52 -4.2 102d-22 " " 3.0 " " " " " " 213 52 152 -4.2 102d-23 " 0 0.5 " " " " " " 135 27 1.74 -6.3 44d-24 " 0.1 " " " " " " " 181 50 1.55 -3.9 104d-25 " 3.0 " " " " " " " 221 57 1.55 -3.8 104d-26 0 0.5 " " " " " " " 95 6 3.65 -6.5 43d-27 0.1 " " " " " " " " 175 51 1.54 -3.8 103d-28 1.0 " " " " " " " " 203 62 1.53 -4.1 108d-29 3.0 " " " " " " " " 206 62 1.54 -4.1 109d-30 0.5 " " " " " " " " 210 54 1.50 -4.5 107__________________________________________________________________________ TABLE 11______________________________________Glass Composition No. B.sub.2 O.sub.3 SiO.sub.2 Ag.sub.2 O______________________________________F1 5 90 5F2 17 80 3F3 30 45 25 (Wt. %)______________________________________ TABLE 12______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 F1 228 73 1.46 -3.9 127 F2 223 73 1.46 -3.8 127 F3 215 73 1.46 -3.9 127b-1 F1 227 74 1.46 -3.9 127 F2 223 75 1.47 -3.8 127 F3 214 74 1.46 -3.9 127______________________________________ TABLE 13______________________________________Glass Compo-sition No. B.sub.2 O.sub.3 SiO.sub.2 Bi.sub.2 O.sub.3 Ag.sub.2 O______________________________________G.sub.1 5 7 85 3G.sub.2 20 10 50 20G.sub.3 25 25 45 5G.sub.4 10 10 55 25______________________________________ (Wt. %) TABLE 14__________________________________________________________________________ ChangeAdditives Glass rate after Thermalcomposition composition C-Value impulse run awayno. No. (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) life (hr)__________________________________________________________________________a-1 G.sub.1 211 74 1.47 -4.1 137 G.sub.2 211 73 1.47 -4.0 139 G.sub.3 210 73 1.47 -4.0 139 G.sub.4 210 74 1.46 -4.0 137b-1 G.sub.1 211 75 1.47 -4.2 137 G.sub.2 210 74 1.47 -4.3 138 G.sub.3 211 74 1.48 -4.3 138 G.sub.4 211 75 1.46 -4.3 137__________________________________________________________________________ TABLE 15______________________________________Glass Compo-sition No. B.sub.2 O.sub.3 SiO.sub.2 Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 Ag.sub.2 O______________________________________J.sub.1 5 5 85 2 3J.sub.2 10 10 60 10 10J.sub.3 25 25 45 2 3J.sub.4 10 10 50 5 25______________________________________ (wt. %) TABLE 16__________________________________________________________________________ ChangeAdditives Glass rate after Thermalcomposition composition C-Value impulse run awayno. No. (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) life (hr)__________________________________________________________________________a-1 J.sub.1 211 83 1.46 -3.5 137 J.sub.2 211 84 1.46 -3.5 138 J.sub.3 214 84 1.47 -3.7 137 J.sub.4 212 85 1.46 -3.8 139b-1 J.sub.1 211 84 1,46 -3.8 138 J.sub.2 212 85 1.47 -3.7 138 J.sub.3 214 86 1.47 -3.9 138 J.sub.4 212 86 1.47 -4.1 139__________________________________________________________________________ TABLE 17__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) value n- test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO Al.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________a-1 0.5 0.5 0.5 1.0 0.5 1.0 0.0025 0 151 46 1.55 -5.8 8a-2 " " " " " " " 0.005 151 46 1.52 -3.0 52a-3 " " " " " " " 0.3 152 47 1.53 -29 53a-4 " " " " " " 0 0.1 151 47 1.83 -6.8 7a-5 " " " " " " 0.0005 " 151 44 1.63 -2.0 53a-6 " " " " " " 0.025 " 157 38 1.64 -2.0 52a-7 " " " " " 0 0.0025 " 150 48 1.38 -4.6 43a-8 " " " " " 0.1 " " 151 49 1.60 -3.5 51a-9 " " " " " 3.0 " " 165 40 1.63 -2.5 54a-10 " " " " 0 1.0 " " 135 51 1.63 -6.8 43a-11 " " " " 0.05 " " " 141 51 1.60 -3.5 53a-12 " " " " 1.5 " " " 173 40 1.63 -3.6 51a-13 " " " 0 0.5 " " " 126 37 1.63 -7.3 44a-14 " " " 0.1 " " " " 134 49 1.58 -3.4 53a-15 " " " 3.0 " " " " 193 53 1.58 -3.3 55a-16 " " 0 1.0 " " " " 103 25 1.84 -7.3 41a-17 " " 0.1 " " " " " 123 46 1.60 -3.4 52a-18 " " 3.0 " " " " " 144 48 1.62 -3.4 54a-19 " 0 0.5 " " " " " 102 25 1.88 -7.2 35a-20 " 0.1 " " " " " " 143 31 1.63 -3.1 57a-21 " 3.0 " " " " " " 163 45 1.64 -3.5 56a-22 0 0.5 " " " " " " 84 6 3.62 -7.3 38a-23 0.1 " " " " " " " 153 38 1.61 -3.3 57a-24 1.0 " " " " " " " 153 55 1.62 -3.3 56a-25 3.0 " " " " " " " 148 54 1.62 -3.4 55a-26 0.5 " " " " " " " 153 52 1.53 -3.3 55__________________________________________________________________________ TABLE 18__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO Gd.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________b-1 0.5 0.5 0.5 1.0 0.5 1.0 0.0025 0 150 47 1.54 -5.5 7b-2 " " " " " " " 0.005 150 46 1.54 -3.1 51b-3 " " " " " " " 0.3 151 47 1.54 -3.1 53b-4 " " " " " " 0 0.1 152 46 1.82 -6.5 7b-5 " " " " " " 0.0005 " 153 43 1.65 -2.1 54b-6 " " " " " " 0.025 " 155 39 1.65 -2.1 52b-7 " " " " " 0 0.0025 " 150 44 1.59 -4.7 41b-8 " " " " " 0.1 " " 150 45 1.61 -3.6 52b-9 " " " " " 3.0 " " 163 40 1.63 -2.5 55b-10 " " " " 0 1.0 " " 134 51 1.62 -6.5 42b-11 " " " " 0.05 " " " 140 50 1.61 -3.4 54b-12 " " " " 1.5 " " " 172 42 1.62 -3.4 52b-13 " " " 0 0.5 " " " 123 36 1.62 -7.1 45b-14 " " " 0.1 " " " " 136 48 1.59 -3.3 55b-15 " " " 3.0 " " " " 191 53 1.59 -3.3 57b-16 " " 0 1.0 " " " " 102 26 1.83 -7.2 42b-17 " " 0.1 " " " " " 121 47 1.61 -3.5 52b-18 " " 3.0 " " " " " 139 47 1.61 -3.4 55b-19 " 0 0.5 " " " " " 101 26 1.83 -7.0 33b-20 " 0.1 " " " " " " 143 32 1.63 -3.0 57b-21 " 3.0 " " " " " " 165 46 1.65 -3.4 56b-22 0 0.5 " " " " " " 85 6 3.55 -7.5 38b-23 0.1 " " " " " " " 153 38 1.62 -3.3 57b-24 1.0 " " " " " " " 152 53 1.61 -3.4 55b-25 3.0 " " " " " " " 150 53 1.63 -3.4 55b-26 0.5 " " " " " " " 150 51 1.56 -3.7 55__________________________________________________________________________ TABLE 19__________________________________________________________________________Additives Glass Change rate ThermalComposition Composition C-Value after impulse run awayNo. No. (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) life (hr)__________________________________________________________________________a-1 A1 158 62 1.53 -3.4 75 A2 155 63 1.53 -3.3 77 A3 159 63 1.53 -3.2 77b-1 A1 159 62 1.56 -3.6 76 A2 155 63 1.56 -3.5 76 A3 153 63 1.56 -3.3 76__________________________________________________________________________ TABLE 20__________________________________________________________________________Additive Glass Change rate ThermalComposition Composition C-Value after impulse run awayNo. No. (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) life (hr)__________________________________________________________________________a-1 B1 151 63 1.54 -3.3 86 B2 153 63 1.53 -3.3 87 B3 153 64 1.53 -3.2 88b-1 B1 151 63 1.57 -3.6 86 B2 153 63 1.56 -3.6 87 B3 153 64 1.56 -3.6 88__________________________________________________________________________ TABLE 21__________________________________________________________________________Additives Glass Change rate ThermalComposition Composition C-Value after impulse run awayNo. No. (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) life (hr)__________________________________________________________________________a-1 E1 151 73 1.53 -3.3 86 E2 152 74 1.54 -3.3 86 E3 153 74 1.54 -3.3 86 E4 154 73 1.54 -3.4 88b-1 E1 151 73 1.55 -3.6 85 E2 152 74 1.56 -3.6 86 E3 153 74 1.56 -3.6 87 E4 153 74 1.56 -3.7 88__________________________________________________________________________ TABLE 22__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- V.sub.100A / test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O (V/mm) Value V.sub. 1mA (%) (hr)__________________________________________________________________________c-1 0.5 0.5 0.5 1.0 0.5 1.0 0.0025 0.1 0 153 52 1.53 -3.3 55c-2 " " " " " " " " 0.0005 152 50 1.52 -3.6 106c-3 " " " " " " " " 0.1 153 52 1.53 -3.3 105c-4 " " " " " " " " 0.3 152 50 1.52 -3.8 109c-5 " " " " " " " 0 0.1 151 50 1.54 -5.4 18c-6 " " " " " " " 0.005 " 151 52 1.53 -3.2 108c-7 " " " " " " " 0.3 " 153 53 1.53 -3.2 108c-8 " " " " " " 0 0.1 " 150 55 1.81 -6.4 17c-9 " " " " " " 0.0005 " " 153 53 1.65 -2.0 105c-10 " " " " " " 0.025 " " 157 43 1.65 -2.0 108c-11 " " " " " 0 0.0025 " " 151 57 1.59 -4.6 42c-12 " " " " " 0.1 " " " 151 56 1.59 -3.5 101c-13 " " " " " 3.0 " " " 167 49 1.62 -2.5 105c-14 " " " " 0 1.0 " " " 136 56 1.62 -6.4 42c-15 " " " " 0.05 " " " " 140 55 1.62 -3.5 102c-16 " " " " 1.5 " " " " 175 51 1.61 -3.4 103c-17 " " " 0 0.5 " " " " 127 37 1.61 -7.0 47c-18 " " " 0.1 " " " " " 134 51 1.58 -3.2 103c-19 " " " 3.0 " " " " " 195 56 1.59 -3.2 105c-20 " " 0 1.0 " " " " " 105 26 1.81 -7.0 45c-21 " " 0.1 " " " " " " 125 51 1.62 -3.4 102c-22 " " 3.0 " " " " " " 145 53 1.61 -3.2 106c-23 " 0 0.5 " " " " " " 104 26 1.85 -6.8 35c-24 " 0.1 " " " " " " " 145 51 1.62 -2.8 101c-25 " 3.0 " " " " " " " 165 55 1.63 -3.4 107c-26 0 0.5 " " " " " " " 84 6 3.53 -7.3 39c-27 0.1 " " " " " " " " 155 41 1.61 -3.1 105c-28 1.0 " " " " " " " " 153 56 1.62 -3.2 106c-29 3.0 " " " " " " " " 149 55 1.63 -3.2 106__________________________________________________________________________ TABLE 23__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O (V/mm) Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________d-1 0.5 0.5 0.5 1.0 0.5 1.0 0.0025 0.1 0 150 51 1.56 -3.7 55d-2 " " " " " " " " 0.0005 153 51 1.54 -3.6 105d-3 " " " " " " " " 0.1 155 51 1.52 -3.5 106d-4 " " " " " " " " 0.3 153 51 1.52 -3.8 108d-5 " " " " " " " 0 0.1 152 50 1.54 -5.3 16d-6 " " " " " " " 0.005 " 152 52 1.53 -3.2 106d-7 " " " " " " " 0.3 " 155 54 1.80 -3.2 106d-8 " " " " " " 0 0.1 " 151 56 1.64 -6.3 17d-9 " " " " " " 0.0005 " " 153 53 1.64 -2.1 106d-10 " " " " " " 0.025 " " 158 43 1.65 -2.1 108d-11 " " " " " 0 0.0025 " " 152 56 1.60 -4.6 12d-12 " " " " " 0.1 " " " 152 55 1.59 -3.6 102d-13 " " " " " 3.0 " " " 169 48 1.61 -2.5 106d-14 " " " " 0 1.0 " " " 138 55 1.62 -6.3 41d-15 " " " " 0.05 " " " " 141 55 1.62 -3.5 103d-16 " " " " 1.5 " " " " 172 52 1.62 -3.6 103d-17 " " " 0 0.5 " " " " 129 38 1.62 -6.9 45d-18 " " " 0.1 " " " " " 136 51 1.58 -3.2 104d-19 " " " 3.0 " " " " " 197 55 1.58 -3.1 106d-20 " " 0 1.0 " " " " " 106 26 1.80 -6.8 43d-21 " " 0.1 " " " " " " 126 50 1.62 -3.3 103d-22 " " 3.0 " " " " " " 147 53 1.61 -3.2 107d-23 " 0 0.5 " " " " " " 105 27 1.82 -6.8 37d-24 " 0.1 " " " " " " " 147 51 1.61 -2.8 101d-25 " 3.0 " " " " " " " 167 55 1.63 -3.3 107d-26 0 0.5 " " " " " " " 85 6 3.88 -7.2 38d-27 0.1 " " " " " " " " 155 42 1.61 -3.0 106d-28 1.0 " " " " " " " " 153 57 1.61 -3.0 106d-29 3.0 " " " " " " " " 151 55 1.61 -3.2 106__________________________________________________________________________ TABLE 24______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 F1 158 73 1.54 -3.4 124 F2 155 73 1.55 -3.4 122 F3 153 73 1.55 -3.4 126b-1 F1 160 73 1.56 -3.6 123 F2 154 73 1.57 -3.6 122 F3 153 73 1.57 -3.7 125______________________________________ TABLE 25______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 G1 151 74 1.53 -3.4 131 G2 151 74 1.53 -3.2 136 G3 153 73 1.53 -3.2 132 G4 151 73 1.53 -3.3 135b-1 G1 150 73 1.56 -3.5 132 G2 150 73 1.56 -3.5 137 G3 153 73 1.56 -3.5 132 G4 150 73 1.56 -3.6 135______________________________________ TABLE 26__________________________________________________________________________Additives Glass Change rate after Thermalcomposition no. composition No. C-Value (V/mm) n-Value V.sub.100A /V.sub.1mA test (%) run away life__________________________________________________________________________ (hr)a-1 J1 150 84 1.53 -3.4 133 J2 150 85 1.53 -3.4 135 J3 153 85 1.53 -3.3 133 J4 151 84 1.54 -3.3 136b-1 J1 151 83 1.56 -3.7 133 J2 151 83 1.56 -3.7 135 J3 153 84 1.56 -3.7 132 J4 151 85 1.57 -3.6 135__________________________________________________________________________ TABLE 27__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________a-1 0.5 0.5 0.5 1.0 0.5 1.0 0.5 0.0025 0 211 51 1.45 -5.1 9a-2 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.005 211 52 1.43 -2.9 151a-3 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 211 53 1.45 -2.7 159a-4 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 210 55 1.75 -6.7 8a-5 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 .dwnarw. 210 53 1.45 -1.9 153a-6 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.025 .dwnarw. 222 43 1.53 -1.9 155a-7 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.0025 .dwnarw. 151 50 1.55 -3.8 57a-8 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. 176 58 1.48 -2.8 151a-9 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 10.0 .dwnarw. .dwnarw. 435 59 1.45 -1.5 154a-10 .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. 210 53 1.50 -4.5 57a-11 .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. 211 52 1.52 -2.5 156a-12 .uparw. .uparw. .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. 233 45 1.55 -1.5 157a-13 .uparw. .uparw. .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. 187 53 1.53 -6.0 63a-14 .uparw. .uparw. .uparw. .uparw. 0.05 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 191 53 1.51 -2.7 151a-15 .uparw. .uparw. .uparw. .uparw. 1.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 235 45 1.55 -2.7 156a-16 .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 176 43 1.53 -6.8 55a-17 .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 185 52 1.48 -2.5 152a-18 .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 245 55 1.49 -2.3 150a-19 .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 148 28 1.75 -6.5 55a-20 .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 201 51 1.51 -2.5 153a-21 .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 210 53 1.52 -2.5 152a-22 .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 133 28 1.75 -6.5 56a-23 .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 178 40 1.55 -2.3 151a-24 .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 217 55 1.55 -2.8 155a-25 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 95 6 3.51 -6.7 65a-26 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 177 41 1.50 -2.3 153a-27 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 205 59 1.51 -2.5 155a-28 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 203 58 1.52 -2.7 155a-29 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 211 52 1.44 -1.7 158__________________________________________________________________________ The symbol .uparw..dwnarw. indicates same amounts TABLE 28__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 (V/mm) Value V.sub.100A /V.sub.1mA (%) (hr)__________________________________________________________________________b-1 0.5 0.5 0.5 1.0 0.5 1.0 0.5 0.0025 0 212 51 1.45 -5.2 9b-2 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.005 212 51 1.45 -2.8 152b-3 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 212 52 1.45 -2.8 158b-4 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 209 55 1.73 -6.9 8b-5 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 .dwnarw. 209 53 1.43 -1.9 153b-6 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.025 .dwnarw. 219 43 1.52 -1.8 153b-7 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.0025 .dwnarw. 150 51 1.56 -3.7 55b-8 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. 178 59 1.49 -2.8 152b-9 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 10.0 .dwnarw. .dwnarw. 426 59 1.46 -1.7 153b-10 .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. 212 54 1.50 -4.7 55b-11 .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. 213 52 1.50 -2.3 156b-12 .uparw. .uparw. .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. 233 41 1.54 -1.8 157b-13 .uparw. .uparw. .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. 175 50 1.54 -6.1 63b-14 .uparw. .uparw. .uparw. .uparw. 0.05 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 186 51 1.51 -2.8 150b-15 .uparw. .uparw. .uparw. .uparw. 1.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 249 43 1.56 -2.8 155b-16 .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 173 43 1.53 -6.9 54b-17 .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 183 50 1.49 -2.5 151b-18 .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 255 50 1.49 -2.1 155b-19 .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 1.49 27 1.75 -6.6 54b-20 .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 203 51 1.51 -2.5 152b-21 .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 213 53 1.51 -2.3 152b-22 .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 132 28 1.77 -6.2 56b-23 .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 178 41 1.55 -2.3 152b-24 .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 221 51 1.54 -2.8 153b-25 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 90 6 3.31 -6.5 67b-26 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 170 40 1.51 -2.1 152b-27 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 207 58 1.51 -2.3 152b-28 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 203 58 1.51 -2.5 152b-29 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 210 51 1.45 -1.8 157__________________________________________________________________________ The symbol .uparw..dwnarw. indicates same amounts TABLE 29______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 A1 232 63 1.45 -1.9 168 A2 225 63 1.45 -1.9 168 A3 221 62 1.44 -1.8 169b-1 A1 231 62 1.44 -1.8 168 A2 225 63 1.44 -1.9 168 A3 219 63 1.44 -1.8 168______________________________________ TABLE 30______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 B1 210 64 1.45 -1.8 179 B2 213 63 1.45 -1.8 178 B3 213 65 1.44 -1.8 178b-1 B1 210 63 1.44 -1.7 178 B2 211 63 1.44 -1.8 178 B3 211 63 1.44 -1.8 178______________________________________ TABLE 31______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 E1 211 75 1.45 -1.8 178 E2 211 73 1.45 -1.8 177 E3 211 75 1.45 -1.7 177 E4 213 75 1.45 -1.7 177b-1 E1 210 74 1.45 -1.7 178 E2 211 74 1.45 -1.8 177 E3 211 73 1.45 -1.7 177 E4 212 75 1.44 -1.9 177______________________________________ TABLE 32__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- V.sub.100A / test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O (V/mm) Value V.sub.1mA (%) (hr)__________________________________________________________________________c-1 0.5 0.5 0.5 1.0 0.5 1.0 0.5 0.0035 0.1 0 211 51 1.45 -1.8 155c-2 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 210 58 1.44 -1.6 191c-3 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 210 59 1.44 -1.5 198c-4 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 211 59 1.44 -1.6 198c-5 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 211 58 1.45 -2.5 18c-6 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.005 .dwnarw. 210 55 1.43 -2.8 192c-7 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 .dwnarw. 210 55 1.44 -2.7 197c-8 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 .dwnarw. 211 55 1.76 -6.5 17c-9 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 .dwnarw. .dwnarw. 211 58 1.46 -1.8 191c-10 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.025 .dwnarw. .dwnarw. 220 50 1.53 -1.9 195c-11 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.0035 .dwnarw. .dwnarw. 153 52 1.53 -3.3 105c-12 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. 177 59 1.48 -2.9 192c-13 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 10.0 .dwnarw. .dwnarw. .dwnarw. 433 59 1.16 -1.5 193c-14 .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. 211 55 1.51 -4.7 106c-15 .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 211 55 1.51 -2.6 193c-16 .uparw. .uparw. .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 235 51 1.56 -1.5 195c-17 .uparw. .uparw. .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 188 55 1.54 -6.3 72c-18 .uparw. .uparw. .uparw. .uparw. 0.05 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 192 55 1.51 -2.7 192c-19 .uparw. .uparw. .uparw. .uparw. 1.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 236 53 1.55 -2.6 193c-20 .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 177 51 1.53 -6.9 64c-21 .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 185 53 1.49 -2.1 193c-22 .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 286 57 1.48 -2.1 197c-23 .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 149 29 1.77 -6.3 65c-24 .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 200 52 1.52 -2.4 193c-25 .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 211 34 1.52 -2.4 197c-26 .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 135 29 1.76 -6.3 66c-27 .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 179 52 1.56 -2.1 195c-28 .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 218 56 1.55 -2.8 198c-29 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 86 6 3.43 -6.5 75c-30 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 178 53 1.51 -2.1 192c-31 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 206 59 1.53 -2.1 196c-32 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 205 59 1.53 -2.5 198__________________________________________________________________________ The symbol .uparw..dwnarw. indicates same amounts TABLE 33__________________________________________________________________________ Change rate Thermal after run C- Impulse awayAdditives (mole %) Value n- V.sub.100A / test lifeNo. Bi.sub.2 O.sub.3 Co.sub.2 O.sub.3 MnO.sub.2 Sb.sub.2 O.sub.3 Cr.sub.2 O.sub.3 NiO SiO.sub.2 Al.sub.2 O.sub.3 B.sub.2 O.sub.3 Ag.sub.2 O (V/mm) Value V.sub.1mA (%) (hr)__________________________________________________________________________d-1 0.5 0.5 0.5 1.0 0.5 1.0 0.5 0.0025 0.1 0 211 52 1.44 -1.9 153d-2 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 209 57 1.44 -1.6 192d-3 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 209 59 1.44 -1.5 179d-4 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 211 59 1.44 -1.7 196d-5 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 211 58 1.45 -2.3 18d-6 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.005 .dwnarw. 210 55 1.43 -2.6 192d-7 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.3 .dwnarw. 211 54 1.44 -2.6 195d-8 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.1 .dwnarw. 211 54 1.75 -6.7 17d-9 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.0005 .dwnarw. .dwnarw. 211 55 1.46 -2.0 192d-10 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.025 .dwnarw. .dwnarw. 223 51 1.52 -2.0 195d-11 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.0025 .dwnarw. .dwnarw. 155 51 1.52 -3.5 106d-12 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. 177 58 1.48 -2.8 192d-13 .uparw. .uparw. .uparw. .uparw. .uparw. .uparw. 10.0 .dwnarw. .dwnarw. .dwnarw. 438 58 1.45 -1.8 194d-14 .uparw. .uparw. .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. 210 54 1.50 -4.5 107d-15 .uparw. .uparw. .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 210 55 1.50 -2.7 193d-16 .uparw. .uparw. .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 237 51 1.56 -1.6 196d-17 .uparw. .uparw. .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. 186 53 1.54 -6.4 73d-18 .uparw. .uparw. .uparw. .uparw. 0.05 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 190 54 1.51 -2.7 193d-19 .uparw. .uparw. .uparw. .uparw. 1.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 230 54 1.55 -2.7 194d-20 .uparw. .uparw. .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 176 52 1.53 -7.0 65d-21 .uparw. .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 184 52 1.49 -2.0 197d-22 .uparw. .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 243 57 1.48 -2.0 197d-23 .uparw. .uparw. 0 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 145 26 1.76 -6.2 65d-24 .uparw. .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 201 52 1.51 -2.4 193d-25 .uparw. .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 212 53 1.51 -2.4 197d-26 .uparw. 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 136 28 1.77 -6.1 67d-27 .uparw. 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 183 50 1.56 -2.0 195d-28 .uparw. 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 219 57 1.55 -2.6 198d-29 0 0.5 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 95 6 3.51 -6.0 75d-30 0.1 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 179 51 1.50 -2.2 192d-31 1.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 206 59 1.50 -2.2 195d-32 3.0 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 206 58 1.50 -2.5 197__________________________________________________________________________ The symbol .uparw..dwnarw. indicates same amounts TABLE 34______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 F1 230 73 1.44 -1.8 217 F2 224 72 1.44 -1.9 218 F3 218 72 1.44 -1.9 217b-1 F1 230 72 1.44 -1.8 217 F2 223 71 1.44 -1.8 217 F3 217 71 1.44 -1.8 217______________________________________ TABLE 35______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 G1 210 73 1.44 -1.8 228 G2 211 73 1.44 -1.8 227 G3 211 73 1.44 -1.8 228 G4 211 72 1.44 -1.9 228b-1 G1 210 73 1.44 -1.8 228 G2 211 73 1.44 -1.8 227 G3 211 73 1.44 -1.8 227 G4 211 72 1.44 -1.9 227______________________________________ TABLE 36______________________________________ ChangeAddi- ratetives Glass after Thermalcompo- compo- C- impulse run awaysition sition Value n- V.sub.100A / test lifeno. No. (V/mm) Value V.sub.1mA (%) (hr)______________________________________a-1 J1 210 84 1.44 -1.5 228 J2 211 85 1.44 -1.4 228 J3 213 85 1.44 -1.4 229 J4 211 84 1.44 -1.5 229b-1 J1 210 83 1.44 -1.5 229 J2 211 83 1.44 -1.4 229 J3 213 83 1.44 -1.5 228 J4 211 83 1.44 -1.5 228______________________________________

Claims

1. A voltage-dependent resistor of bulk-type comprising a sintered body consisting essentially of, as a main constituent, zinc oxide (ZnO) and, as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and at least one member selected from the group of 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2) with electrodes applied to opposite surfaces of said sintered body.

2. A voltage-dependent resistor of bulk-type comprising a sintered body consisting essentially of, as a main constituent, zinc oxide (ZnO) and, as additives, 0.1 to 3.0 mole percent of bismuth oxide (Bi.sub.2 O.sub.3), 0.1 to 3.0 mole percent of cobalt oxide (Co.sub.2 O.sub.3), 0.1 to 3.0 mole percent of manganese oxide (MnO.sub.2), 0.1 to 3.0 mole percent of antimony oxide (Sb.sub.2 O.sub.3), 0.05 to 1.5 mole percent of chromium oxide (Cr.sub.2 O.sub.3), 0.0005 to 0.3 mole percent of boron oxide (B.sub.2 O.sub.3), at least one member selected from the group of 0.0005 to 0.025 mole percent of aluminum oxide (Al.sub.2 O.sub.3) and 0.0005 to 0.025 mole percent of gallium oxide (Ga.sub.2 O.sub.3), and at least one member selected from the group of 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.1 to 10.0 mole percent of silicon oxide (SiO.sub.2) and 0.0005 to 0.3 mole percent of silver oxide (Ag.sub.2 O), with electrodes applied to opposite surfaces of said sintered body.