Information
-
Patent Grant
-
6245433
-
Patent Number
6,245,433
-
Date Filed
Wednesday, May 12, 199925 years ago
-
Date Issued
Tuesday, June 12, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Jones; Deborah
- McNeil; Jennifer
Agents
- Ostrolenk, Faber, Gerb & Soffen, LLP
-
CPC
-
US Classifications
Field of Search
US
- 428 469
- 428 697
- 428 471
- 428 702
- 428 701
- 501 134
- 501 135
- 501 136
- 501 137
- 501 138
- 501 139
- 361 3214
- 361 3215
- 361 3063
- 361 313
- 361 309
- 361 3011
- 361 311
- 361 320
- 361 3212
- 361 3213
-
International Classifications
-
Abstract
A dielectric ceramic composition containing a primary component represented by the following formula: {BaO}mTiO2+αM2O3+βR2O3+γBaZrO3+gMgO+hMnO wherein M2O3 is at least one of Sc2O3 or Y2O3; R2O3 is at least one member selected from the group consisting of Eu2O3, Gd2O3, Tb2O3. Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3; α, β, γ, g or h represent a mole ratio and satisfy specified relations; and silicon oxide as an auxiliary component in an amount of 0.2-5.0 mol as SiO2, with respect to 100 mol of the primary component.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric ceramic composition and a laminated ceramic capacitor.
2. Background Art
A laminated ceramic capacitor is generally produced through the following procedure.
Briefly, a dielectric material sheet is prepared and a material for forming an internal electrode is applied thereto. A composition predominantly comprising BaTiO
3
may be used as the dielectric material. Subsequently, sheets of dielectric material to which the electrode material has been applied are laminated and compressed with heating, and the resultant substance is fired at 1250-1350° C. in air to thereby obtain a laminated ceramic having internal electrodes. Finally, external electrodes are baked onto both sides of the laminated ceramic so that the external electrodes can be connected to the internal electrodes to thereby obtain a laminated ceramic capacitor.
Noble metal such as platinum, gold, palladium or silver-palladium alloy has been used for the material of an internal electrode of a laminated ceramic capacitor. Although each of these metals has excellent properties required of a electrode material, these metals are expensive and increase manufacturing cost. Therefore, a laminated capacitor in which nickel, a base metal, is used for internal electrodes has been proposed so as to reduce manufacturing cost, and nickel has increasingly been used.
As electronic devices have become smaller in size, cheaper in price and of higher performance, the laminated ceramic capacitor is also required to be cheaper, more insulation-resistant from voltage breakdown, more insulated, more reliable and of higher capacitance. In order to reduce the price of electronic devices, a laminated ceramic capacitor in which nickel is used for internal electrodes is advantageously used because of its low price. However, conventional dielectric ceramic materials were designed to be used in a weak electric field only and they involve a problem in that insulation resistance, dielectric strength and reliability are drastically decreased when they are used in a strong electric field. No known laminated ceramic capacitor whose internal electrodes are formed of nickel can be used in a strong electric field.
More specifically, Japanese Patent Publication (kokoku) No. 42588/1982 and Japanese Patent Application Laid-Open (kokai) No. 101459/1986 disclose dielectric materials which have a high dielectric constant. However, the obtained dielectric ceramics have large crystal grains, resulting in disadvantages such as low dielectric strength of a laminated ceramic capacitor under a strong electric field and a short life in a high-temperature test.
Japanese Patent Publication (kokoku) No. 14611/1986 and Japanese Patent Application Laid-Open (kokai) No. 272971/1995 disclose dielectric materials which have high dielectric constants of 2000 or more and 3000 or more under a weak electric field, respectively. However, these materials have several disadvantages, such as a considerably low dielectric constant (electrostatic capacity) and low insulation resistance under a strong electric field. These materials comprise Li
2
O—SiO
2
or B
2
O
3
—SiO
2
oxide serving as an additive component and these oxides diffuse while firing, causing lot-to-lot variation in electrical properties of fired products.
Accordingly, an object of the present invention is to provide a dielectric ceramic composition which can constitute a dielectric ceramic layer of a laminated ceramic capacitor, which has high weather resistance such as durability under high-temperature or good resistance in a humid environment, and which also has the following electric properties: the product of insulation resistance and electrostatic capacity represented by C×R is as high as 5000 Ω·F or more at room temperature and 200 Ω·F or more at 150° C. under a strong electric field of 10 kV/mm, insulation resistance exhibits low dependence on voltage, electrostatic capacity is highly stable with respect to a change of DC bias voltage, dielectric strength is high and the rate of change in electrostatic capacity with temperature satisfies the B characteristic specified by JIS specifications and X7R characteristic specified by EIA specifications. Another object of the present invention is to provide a laminated ceramic capacitor comprising an internal electrode constituted by Ni or Ni alloy and the aforementioned dielectric ceramic composition serving as a dielectric ceramic layer.
SUMMARY OF THE INVENTION
In order to attain the aforementioned objects, in one aspect of the present invention, there is provided a dielectric ceramic composition comprising a primary component formed of barium zirconate, magnesium oxide, manganese oxide, barium titanate having an alkali metal oxide content of 0.02 wt % or less and at least one member selected from the group consisting of europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide and ytterbium oxide; the primary component being represented by the following formula: {BOA}
m
TiO
2
+βR
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein R
2
O
3
is at least one member selected from the group consisting of Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, Ho
2
O
3
, Er
2
O
3
, Tm
2
O
3
and Yb
2
O
3
, and each of β, γ, g and h represents a mole ratio and satisfy the following relations;
0.001≦α≦0.06;
0.005≦γ≦0.06;
0.001<g≦5 0.12;
0.001<h≦0.12;
g+h≦0.13; and
1.000<m≦1.035,
and further comprises silicon oxide as an auxiliary component in an amount of 0.2-5.0 mol calculated as SiO
2
, with respect to 100 mol of the primary component.
In another aspect of the present invention, there is provided a dielectric ceramic composition which comprises a primary component formed of barium titanate having an alkali metal oxide content of 0.02 wt % or less, at least one of scandium oxide or yttrium oxide, barium zirconate, magnesium oxide and manganese oxide, and represented by the following formula: {BOA}
m
TiO
2
+αM
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein M
2
O
3
is at least one of Sc
2
O
3
or Y
2
O
3
, and α, γ, g and h each represents a mole ratio and satisfy the following relations:
0.001≦α≦0.06;
0.001≦γ≦0.06;
0.001<g≦0.12;
0.001<h≦0.12;
g+h≦0.13; and
1.000<m≦1.035,
and further comprises silicon oxide as an auxiliary component in an amount of 0.2-5.0 mol as SiO
2
, with respect to 100 mol of the primary component.
Further, in still another aspect of the present invention, there is provided a dielectric ceramic composition which comprises a primary component formed of barium titanate having an alkali metal oxide content of 0.02 wt % or less, barium zirconate, magnesium oxide, manganese oxide, at least one of scandium oxide or yttrium oxide, and at least one member selected from the group consisting of europium oxide, gadolinium oxide, terbium oxide and dysprosium oxide; the primary component being represented by the following formula: {Bao}
m
TiO
2
+αM
2
O
3
+βR
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein M
2
O
3
is at least one of Sc
2
O
3
or Y
2
O
3
, R
2
O
3
is at least one member selected from the group consisting of Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, and Dy
2
O
3
, and α, β, γ, g or h each represent a mole ratio and satisfy the following relations;
0.001≦α≦0.05;
0.001≦β≦0.05;
0.005≦γ≦0.06;
0.001<g≦0.12;
0.001<h≦0.12;
α+β≦0.06
g+h≦0.13; and
1.000<m≦1.035,
and further comprises silicon oxide as an auxiliary component in an amount of 0.2-5.0 mol as SiO
2
, with respect to 100 mol of the primary component.
The present invention is also directed to a laminated ceramic capacitor comprising a plurality of dielectric ceramic layers, internal electrodes formed between the dielectric ceramic layers and external electrodes electrically connected to the internal electrodes. In such a laminated ceramic capacitor, the dielectric ceramic layers are formed of the aforementioned dielectric ceramic composition of the present invention and the internal electrodes are formed of nickel or a nickel alloy.
In the laminated ceramic capacitor of the present invention, the external electrodes may comprise a first layer of conductive metal powder or glass frit-added conductive metal powder which has been sintered; and a second layer which is a plating layer provided on the first layer.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other objects, features, and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood with reference to the following detailed description of the preferred embodiments when considered in connection with accompanying drawings, in which:
FIG. 1
a sectional view of an example of a laminated ceramic capacitor;
FIG. 2
is a plan view of a dielectric ceramic layer having an internal electrode in the laminated ceramic capacitor of
FIG. 1
; and
FIG. 3
is an exploded perspective view of a laminated ceramic in the laminated ceramic capacitor of FIG.
1
.
BEST MODES FOR CARRYING OUT THE INVENTION
A basic structure of the laminated ceramic capacitor in one embodiment of the present invention will be described by reference of the figures.
As shown in
FIG. 1
, a laminated ceramic capacitor
1
of the embodiment comprises a rectangular laminated ceramic
3
which is obtained by laminating a plurality of dielectric ceramic layers
2
a
and
2
b
in which the layers have internal electrodes
4
between them. Additionally, external electrodes
5
are formed onto the both side faces of the laminated ceramic
3
such that they are connected to the specific internal electrodes
4
. First layers
6
, which comprise plating such as Ni or copper, are formed onto the external electrodes
5
, and second layers
7
, which comprises plating such as solder or tin, are formed onto the first layers
6
.
The manufacturing process of the laminated ceramic capacitor
1
will next be described in the order of manufacturing steps.
First, raw powder material of barium titanate is provided. The raw material is to provide a mixture of any one of the following three types of primary components and silicon oxide serving as an auxiliary component and is to form dielectric ceramic layers
2
a
and
2
b
. The ingredients are weighed in predetermined proportions and mixed. The following three powder materials for producing dielectric ceramic compositions are prepared:
a material which comprises barium titanate containing alkali metal oxide in an amount of 0.02 wt % or less; at least one oxide selected from the group consisting of europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide and ytterbium oxide; barium zirconate; magnesium oxide; and manganese oxide;
a material which comprises barium titanate containing alkali metal oxide in an amount of 0.02 wt % or less; at least one oxide selected from scandium oxide and yttrium oxide; barium zirconate; magnesium oxide; and manganese oxide; and
a material which comprises barium titanate containing alkali metal oxide in an amount of 0.02 wt % or less; at least one of scandium oxide or yttrium oxide, at least one element selected from the group consisting of europium oxide, gadolinium oxide, terbium oxide and dysprosium oxide; barium zirconate; magnesium oxide; and manganese oxide.
Subsequently, an organic binder is added into the weighed powder materials so as to prepare slurries. Each slurries is formed into a sheet to obtain green sheets for dielectric ceramic layers
2
a
and
2
b.
Subsequently, an internal electrode
4
formed of nickel or an nickel alloy is formed on the main surface of the green sheet serving as a dielectric ceramic layer
2
b
. When the dielectric ceramic layers
2
a
and
2
b
are formed by use of the aforementioned dielectric ceramic composition, nickel or a nickel alloy can be used for forming the internal electrode
4
. The internal electrode
4
may be formed through a method such as screen printing, vapor deposition, or plating.
Subsequently, green sheets serving as the dielectric ceramic layers
2
b
having internal electrodes
4
are laminated as desired, and the resultant laminated product is sandwiched by two green sheets having no internal electrode serving as dielectric ceramic layers
2
a
shown in
FIG. 3
, and the product is compressed to thereby obtain a green laminated ceramic.
The green laminated ceramic is fired at a predetermined temperature in a reducing atmosphere to thereby obtain a laminated ceramic
3
.
Subsequently, external electrodes
5
are formed on both side faces of the laminated ceramic
3
such that they are electrically connected to the internal electrodes
4
. The external electrodes
5
may be formed of a material identical to that of the internal electrodes
4
. Examples of the material which may be used include silver, palladium, silver-palladium alloys, copper, copper-alloys and powders of these metals or alloys to which a glass frit formed of B
2
O
3
—SiO
2
—BaO glass, Li
2
O—SiO
2
—BaO glass, etc. is added. The material is appropriately selected in consideration of the application and site for employing the laminated ceramic capacitors. The external electrodes
5
are formed by applying a metal powder paste as an electrode material to the laminated ceramic
3
which is obtained by firing and further baking. Alternatively, the paste may be applied to the laminated ceramic
3
before firing and then the entirety may be baked.
Subsequently, the external electrodes
5
are plated with nickel, copper, etc., to thereby form first plating layers
6
. Finally, second plating layers
7
formed of solder, tin, etc. are formed on the first plating layers
6
, to produce a laminated ceramic capacitor
1
. Such formation of metal layers on the external electrodes
5
may be omitted depending on the application of laminated ceramic capacitors.
As described hereinabove, the above-described dielectric ceramic composition does not deteriorate the properties of the laminated ceramic capacitor when the composition is fired in a reducing atmosphere in order to form dielectric ceramic layers
2
a
and
2
b
. Thus, the ceramic capacitor had excellent properties described below. That is, when the capacitor is used under high electric field of 10 kV/mm, the product of insulation resistance and electrostatic capacity represented by C×R is as high as 5000 Ω·F or more at room temperature and 200 Ω·F or more at 150° C. The dependence of insulation resistance on voltage is low. The absolute value of rate of reduction in capacitance is as low as 45% or less when DC voltage of 5 kV/mm is applied. The breakdown voltage is high. The temperature characteristics of electrostatic capacity satisfy the B characteristic specified by JIS specifications within a range of −25° C. to +85° C. and satisfy the X7R characteristic specified by EIA specifications within a range of −55° C. to +125° C. The resistance properties as determined under load of high temperature at 25 kV/mm (DC) and 150° C. and in high humidity are excellent.
Impurities contained in barium titanate, which is one of the primary components of the dielectric ceramic composition, include alkaline earth metal oxides such as SrO or CaO, alkali metal oxides such as Na
2
O or K
2
O, and other oxides such as Al
2
O
3
or SiO
2
. Among them, in particular, the alkali metal oxide has been confirmed to affect electric characteristics thereof. However, the relative dielectric constant can be maintained at 1000 or more by adjusting the content of alkali metal oxide to 0.02 wt. % or less, to thereby use the dielectric ceramic composition in practice without any problem.
Silicon oxide serving as an auxiliary component is added to the dielectric ceramic composition, since the oxygen partial pressure in a firing atmosphere is adjusted to an oxygen partial pressure at equilibrium of Ni/NiO at a relatively high temperature state during the firing step, to thereby enhance sinterability and resistance characteristics in humid conditions. In addition, silicon oxide, which is different from an oxide such as Li
2
O—Si
2
O or B
2
O
3
—SiO
2
, has excellent dispersibility in a green sheet and does not evaporate during firing, to thereby attain uniform lot-to-lot electric characteristics of fired ceramics.
EXAMPLES
The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto.
Example 1
Titanium tetrachloride (TiCl
4
) and barium nitrate (Ba(NO
3
)
2
) samples having a variety of purities were prepared as starting materials and weighed. Oxalic acid was added to precipitate titanyl barium oxalate (chemical formula: {BaTiO(C
2
O
4
)·4H
2
O}). The precipitate was decomposed with heat at 1000° C. or more to thereby prepare the four types of barium titanate (BaTiO
3
) shown in Table 1.
TABLE 1
|
|
Type of
Impurity content (wt. %)
Average
|
barium
Alkali
particle
|
titanate
metal
size
|
(BaTiO
3
)
oxide
SrO
CaO
SiO
2
Al
2
O
3
(μm)
|
|
A
0.003
0.012
0.001
0.01
0.005
0.6
|
B
0.02
0.01
0.003
0.019
0.008
0.56
|
C
0.012
0.179
0.018
0.155
0.071
0.72
|
D
0.062
0.014
0.001
0.019
0.004
0.58
|
|
BaCO
3
and several types of oxides having purity of 99% or more were prepared. The oxides included Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, Ho
2
O
3
, Er
2
O
3
, Tm
2
O
3
, Yb
2
O
3
, BaZrO
3
, MgO, and MnO. BaCO
3
was used for adjusting the mole ratio of Ba/Ti in the barium titanate.
Colloidal silica comprising 20 wt. % silicon oxide calculated as SiO
2
was also prepared as an auxiliary component.
These powder materials and the silicon oxide serving as an auxiliary component were weighed to prepare the compositions shown in Table 2. The amount of added silicon oxide is represented as an amount by mol with respect to 100 mol of the primary component, [{BaO}
m
TiO
2
+βR
2
O
3
+γBaZrO
3
+gMgO+hMnO].
TABLE 2
|
|
{BaO}
m
•TiO
2
+ βR
2
O
3
+ γBaZrO
3
+ gMgO + hMnO
|
Sample
Type of
β
SiO
2
|
No.
BaTiO
3
Eu
2
O
3
Gd
2
O
3
Tb
2
O
3
Dy
2
O
3
Ho
2
O
3
Er
2
O
3
Tm
2
O
3
Yb
2
O
3
Total β
γ
g
h
g + h
m
(mol)
|
|
*1
A
0
0
0
0.0008
0
0
0
0
0.0008
0.03
0.07
0.01
0.08
1.005
3
|
*2
A
0
0.04
0
0
0.03
0
0
0
0.07
0.02
0.03
0.09
0.12
1.01
2
|
*3
A
0
0.02
0
0
0
0.02
0
0
0.04
0
0.05
0.04
0.09
1.01
2
|
*4
A
0
0
0.01
0.02
0
0
0
0
0.03
0.08
0.02
0.02
0.04
1.005
1.5
|
*5
A
0
0.02
0
0
0
0
0
0
0.02
0.03
0.001
0.049
0.05
1.005
1
|
*6
A
0.02
0
0
0.03
0
0
0
0.01
0.06
0.01
0.125
0.002
0.127
1.01
4
|
*7
A
0
0
0.01
0
0
0
0.01
0
0.02
0.04
0.039
0.001
0.04
1.01
2
|
*8
A
0
0
0.04
0
0
0.02
0
0
0.06
0.01
0.002
0.125
0.127
1.01
1
|
*9
A
0
0.02
0.03
0
0.01
0
0
0
0.06
0.04
0.05
0.11
0.16
1.01
2
|
*10
A
0
0
0.02
0
0
0
0
0
0.02
0.02
0.01
0.03
0.04
0.99
1
|
*11
A
0
0
0
0.03
0
0
0
0
0.03
0.05
0.04
0.02
0.06
1
2
|
*12
A
0
0
0
0
0
0
0.01
0
0.01
0.01
0.01
0.01
0.02
1.04
4
|
*13
A
0
0
0.01
0
0.01
0
0
0
0.02
0.01
0.01
0.01
0.02
1.01
0
|
*14
A
0
0
0.01
0
0
0
0.02
0
0.03
0.04
0.03
0.03
0.06
1.01
0.1
|
*15
A
0
0
0
0
0.04
0
0
0
0.04
0.03
0.1
0.01
0.11
1.01
8
|
*16
D
0
0
0
0.02
0
0.01
0
0
0.03
0.02
0.03
0.01
0.04
1.01
2
|
17
B
0
0
0
0
0.02
0
0
0
0.02
0.02
0.02
0.01
0.03
1.005
1
|
18
C
0
0.02
0
0
0
0
0.01
0
0.03
0.02
0.03
0.02
0.05
1.015
1.5
|
19
A
0.02
0
0
0.03
0
0
0
0
0.05
0.03
0.002
0.12
0.122
1.01
1.5
|
20
A
0
0.001
0
0
0
0
0
0
0.001
0.03
0.11
0.02
0.13
1.01
4
|
21
A
0
0
0.02
0.04
0
0
0
0
0.06
0.02
0.005
0.01
0.015
1.01
3
|
22
A
0
0.01
0
0
0
0.01
0
0
0.02
0.005
0.03
0.02
0.05
1.01
1.5
|
23
A
0
0
0
0.01
0
0
0.01
0
0.02
0.06
0.01
0.03
0.04
1.005
1
|
24
A
0
0
0
0.02
0
0.01
0
0
0.03
0.03
0.02
0.04
0.06
1.035
3
|
25
A
0
0.01
0
0
0.01
0
0
0
0.02
0.03
0.005
0.045
0.05
1.015
0.2
|
26
A
0
0
0
0
0.01
0
0
0
0.01
0.03
0.12
0.002
0.122
1.01
5
|
27
A
0.01
0
0
0
0
0.01
0
0
0.02
0.02
0.02
0.02
0.04
1.01
1.5
|
28
A
0
0
0.01
0
0
0
0
0
0.01
0.02
0.015
0.005
0.02
1.01
1.5
|
29
A
0.01
0
0
0
0
0.01
0
0
0.02
0.03
0.01
0.04
0.05
1.01
1.5
|
|
Samples marked with * are beyond the scope of present invention.
|
Subsequently, organic solvents such as polyvinyl butyral binder and ethanol were added to the weighed materials and the resultant mixture was wet-mixed by use of a ball mill so as to prepare a ceramic slurry. The ceramic slurry was formed into a sheet by use of a doctor blade to obtain a green rectangular sheet having a thickness of 35 μm. After the above process, a conductive paste predominantly comprising nickel was applied to a surface of the ceramic green sheet so as to form a conductive paste layer for constituting an internal electrode.
The ceramic green sheets having conductive paste layers formed thereon were laminated so that leading ends of the conductive paste films on the ceramic green sheet were arranged alternately in order to obtain a laminated substrate. The laminated substrate was heated at 350° C. in a nitrogen atmosphere to decompose the binder, and fired at a temperature shown in Table 3 for two hours in a reducing atmosphere of H
2
—N
2
—H
2
O gas containing oxygen at a partial pressure of 10
−9
-10
−12
MPa so as to obtain a ceramic sintered body.
After firing, a silver paste comprising B
2
O
3
—Li
2
O—SiO
2
—BaO glass frit was applied to the surface of each side of the obtained ceramic sintered body, followed by firing in a nitrogen atmosphere at 600° C. to form external electrodes electrically connected to the internal electrodes.
The laminated ceramic capacitor obtained by the above processes had a width of 5.0 mm, a length of 5.7 mm and a thickness of 2.4 mm, and dielectric ceramic layers each had a thickness of 30 μm. The total number of effective dielectric ceramic layers was 57 and the area of opposing electrodes per layer was 8.2×10
−5
m
2
.
Subsequently, a nickel plating solution comprising nickel sulfate, nickel chloride and boric acid was prepared to form nickel plating layers on the surface of the external electrodes by use of a barrel plating method. Finally, a solder plating solution prepared from an AS (alkanol sulfonic acid) bath was prepared to form solder plating layers on the nickel plating layers by use of a barrel plating method.
After formation of these laminated ceramic capacitors, their electric characteristics were measured. Electrostatic capacity (C) and dielectric loss (tan δ) were measured at 1 kHz, 1 Vrms and 25° C. by use of an automatic bridge instrument so as to calculate dielectric constant (∈) from electrostatic capacity. Subsequently, insulation resistance (R) was measured at 25° C. and 150° C. by application of direct-current voltages of 315 V (i.e. 10 kV/mm) and 945 V (i.e. 30 kV/mm) by use of an insulation resistance tester so as to obtain C×R, which represents the product of electrostatic capacity and insulation resistance.
The laminated ceramic capacitor was also evaluated for the rate of change in electrostatic capacity with temperature. The rate of change in electrostatic capacity was measured at −25° C. and 85° C., with the electrostatic capacity at 20° C. being used as a standard (ΔC/C
20
), and at −55° C. and 125° C. with the electrostatic capacity at 25° C. being used as a standard (ΔC/C
25
). The maximum absolute value of rate of change in electrostatic capacity was also measured in a range between −55° C. and 125° C. (|ΔC|max).
The laminated ceramic capacitor was also evaluated for DC bias characteristic. Electrostatic capacity was measured under application of an AC voltage of 1 kHz and 1 Vrms. Electrostatic capacity was also measured under simultaneous application of DC 150 V and an AC voltage of 1 kHz and 1 Vrms. The rate of reduction in electrostatic capacity (ΔC/C) induced by DC voltage was calculated.
In a high temperature test, the time-course change of insulation resistance was measured under application of 750 V DC (i.e. 25 kV/mm) at 150° C. for 36 capacitors for each sample. In a durability test under high temperature, the time until the insulation resistance of the capacitors fell to 10
5
Ω or less was regarded the life, and the average life of the capacitors was calculated.
In a humidity resistance test, a DC voltage of 315 V was applied to 72 capacitors of each sample for 250 hours at 120° C. and a pressure of 2 atmospheres (relative humidity: 100%) so as to count the number of capacitors for each sample No. having insulation resistance of 10
6
Ω or less.
Breakdown voltage was also measured by application of AC or DC voltage at a voltage elevation rate of 100 V/sec, and breakdown voltage for both AC voltage and DC voltage was measured.
The results are shown in Table 3.
TABLE 3
|
|
DC bias
|
Rate of change in capacitance with
characteristic
|
Firing
Dielectric
temperature (%)
(%)
|
Sample
temperature
Dielectric
loss:
ΔC/C
20
ΔC/C
25
Maximum
ΔC/C
25
|
No.
(° C.)
constant
tan δ (%)
−25° C.
85° C.
−55° C.
125° C.
value
5 kV/mm
|
|
*1
1300
1900
0.8
2.0
−8.7
4.2
−12.6
13.3
−50
|
*2
1300
840
0.9
3.6
−14.8
6.6
−23.3
23.5
−13
|
*3
1280
1340
0.9
3.5
−8.6
3.2
−13.5
13.5
−31
|
*4
1300
1400
1
3.6
−13.1
4.1
−28.5
28.7
−35
|
*5
1280
1530
0.9
3.5
−13.3
3.9
−17.3
17.3
−42
|
*6
1360
970
2.6
3
−9
4.6
−12.7
12.9
−15
|
*7
Not measurable because of semiconductivity
|
*8
1280
1080
0.8
4.3
−9.1
4.6
−18.2
18.4
−15
|
*9
1280
1020
2.5
3
−9.1
4
−13.6
13.6
−16
|
*10
Not measurable because of semiconductivity
|
*11
1300
1450
1
3.3
−9.5
3.7
−13.5
13.5
−39
|
*12
Not measurable because of poor sintering
|
*13
Not measurable because of poor sintering
|
*14
1360
1470
0.8
3.4
−9.4
3.9
−13
13
−39
|
*15
1280
1020
0.9
3.3
−13.1
3.9
−28.4
28.4
−14
|
*16
1300
1050
0.8
2.9
−8.8
4.1
−13.6
13.6
−16
|
17
1280
1570
0.8
2.6
−9.1
3.7
−13.7
13.7
−41
|
18
1280
1480
0.8
2.9
−8.9
3.8
−13.1
13.1
−37
|
19
1300
1150
0.7
3.3
−8.9
4.1
−13.7
13.7
−17
|
20
1300
1660
0.9
3.3
−9
3.9
−13.7
13.7
−44
|
21
1300
1030
0.7
3.4
−9.2
3.9
−13.7
13.7
−14
|
22
1300
1560
0.7
3.1
−9.2
3.7
−13.6
13.6
−40
|
23
1280
1550
0.7
3.1
−8.9
4.1
−12.7
12.7
−40
|
24
1280
1440
0.7
3.4
−9
4
−13.1
13.1
−36
|
25
1300
1560
0.7
4.1
−8.7
4
−13.6
13.6
−40
|
26
1300
1500
0.7
4
−8.8
3.8
−13.6
13.6
−42
|
27
1300
1510
0.8
3.5
−8.6
4.2
−12.8
12.8
−41
|
28
1300
1580
0.7
3.3
−8.9
3.6
−13.5
13.5
−42
|
29
1280
1550
0.7
3.4
−8.8
3.5
−13
13
−42
|
|
Number of
|
defective
|
C × R (Ω · F)
Breakdown
capacitors in
|
Application
Application
Application
Application
voltage
humidity
|
Sample
of 315 V
of 945 V
of 315 V
of 945 V
(kV/mm)
resistance
Average
|
No.
25° C.
150° C.
AC
DC
test
life (h)
|
|
*1
3020
2870
120
120
13
14
0/72
840
|
*2
5090
4840
220
210
12
14
0/72
180
|
*3
3000
2090
130
90
12
14
0/72
800
|
*4
5140
4880
220
210
12
14
0/72
130
|
*5
3020
2870
130
120
13
14
0/72
870
|
*6
5100
4850
220
210
13
14
51/72
190
|
*7
Not measurable because of semiconductivity
|
*8
3080
2930
120
110
12
14
0/72
120
|
*9
5060
4810
240
230
12
14
19/72
90
|
*10
Not measurable because of semiconductivity
|
*11
3160
3000
180
170
10
11
0/72
180
|
*12
Not measurable because of poor sintering
|
*13
Not measurable because of poor sintering
|
*14
3140
2980
170
160
12
14
34/72
810
|
*15
3270
3110
150
140
13
14
0/72
830
|
*16
5120
4860
260
250
13
15
0/72
840
|
17
5080
4830
250
240
12
14
0/72
930
|
18
5120
4870
220
210
13
15
0/72
900
|
19
5200
4940
260
250
13
15
0/72
890
|
20
5280
5020
220
210
12
14
0/72
840
|
21
5080
4830
230
220
13
14
0/72
890
|
22
5100
4840
270
260
13
15
0/72
840
|
23
5200
4940
230
220
12
15
0/72
800
|
24
5260
5000
260
250
12
14
0/72
870
|
25
5180
4920
220
210
12
14
0/72
800
|
26
5110
4860
240
230
12
14
0/72
880
|
27
5260
5000
290
280
12
14
0/72
830
|
28
5270
4990
260
250
13
14
0/72
870
|
29
5140
4880
290
280
13
14
0/72
890
|
|
Samples marked with * are beyond the scope of the present invention
|
As is clearly shown in Tables 1 through 3, the laminated ceramic capacitors of the present invention provide the following results: the rate of reduction in capacitance was −45% or less under application of a DC voltage of 5 kV/mm, dielectric loss was 1.0% or less, and the rate of change in electrostatic capacity with temperature satisfied the B characteristics specified by JIS specifications within a range of −25° C. to +85° C., and satisfied the X7R characteristics specified by EIA specifications within a range of −55° C. to +125° C.
When the laminated ceramic capacitor was used under a strong electric field of 10 kV/mm, insulation resistance represented by C×R was as high as 5000 Ω·F or more at 25° C., and 200 Ω·F or more at 150° C. Breakdown voltage was as high as 12 kV/mm or more under application of AC voltage, and 14 kV/mm or more under application of DC voltage. In an accelerated test under 25 kV/mm at 150° C., the capacitor had a long life of 800 hours or longer and could be fired at a relatively low temperature of 1300° C. or lower. There was little difference in electric properties between lots of capacitors, which are not shown in any tables.
Next will be described the reason why the composition of the present invention is limited as described.
The composition of the present invention has the formula {BaO}
m
TiO
2
+βR
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein R
2
O
3
is at least one member selected from the group consisting of Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, Ho
2
O
3
, Er
2
O
3
, Tm
2
O
3
, and Yb
2
O
3
, and β, γ, g and h each represent a mole ratio. When the R
2
O
3
content represented by β is less than 0.001 as in the case of Sample No. 1, insulation resistance and C×R are disadvantageously low. When β is more than 0.06 as in the case of Sample No. 2, temperature-dependent characteristics fail to satisfy the B and X7R characteristics to yield poor reliability. Therefore, β preferably falls within a range of 0.001≦β≦0.06.
When the BaZrO
3
content represented by γ is 0 as in the case of Sample No. 3, insulation resistance is low and voltage dependence of insulation resistance is unfavorably high, as compared with samples including BaZrO
3
. When γ is more than 0.06 as in the case of Sample No. 4, temperature-dependent characteristics fail to satisfy the B and X7R characteristics and the average life is disadvantageously short. Therefore, γ preferably falls within a range of 0.005≦γ≦0.06.
When the MgO content represented by g is 0.001 as in the case of Sample No. 5, insulation resistance is low, and temperature-dependent characteristics fail to satisfy B and X7R characteristics. When g is more than 0.12 as in the case of Sample No. 6, unfavorable results are obtained, such as high sintering temperature, dielectric loss of more than 2.0%, extreme increase in defective rate of capacitors in a humidity resistance test and short average life. Therefore, g preferably falls within a range of 0.001<g≦0.12.
When the MnO content represented by h is 0.001 as in the case of Sample No. 7, measurement is impossible because the capacitors exhibit a semi-conducting property. When h is in excess of 0.12 as in the case of Sample No. 8, temperature-dependent characteristics fail to satisfy the X7R characteristics, and insulation resistance is disadvantageously low and the average life is short. Therefore, h preferably falls within a range of 0.001<h≦0.12.
When the total amount of MgO and MnO represented by g+h is more than 0.13 as in the case of Sample No. 9, unfavorable results are obtained, such as high dielectric loss of 2.0% or more, short average life, and an increase in the defectives rate of capacitors in the humidity resistance test. Therefore, g+h is preferably 0.13 or less.
When the ratio of BaO/TiO
2
represented by m is less than 1.000 as in the case of Sample No. 10, measurement is impossible because the capacitors exhibit a semiconducting property. When m is 1.000 as in the case of Sample No. 11, unfavorable results are obtained, such as low insulation resistance, low insulation breakdown voltage under application of AC and DC voltage and short average life. When m is more than 1.035 as in the case of Sample No. 12, measurement is impossible because of poor sintering. Therefore, m preferably falls within a range of 1.000<m≦1.035.
When the SiO
2
content is zero as in the case of Sample No. 13, sintering is poor. When the SiO
2
content is less than 0.2 mol as in the case of Sample No. 14, insulation resistance decreases with increase of sintering temperature and the defectives rate of capacitors becomes considerably high in the humidity resistance test. When the SiO
2
content is more than 5.0 mol, dielectric constant decreases, temperature-dependent characteristics fail to satisfy the X7R characteristics, and C×R fails to satisfy 5000 Ω·F or more at 25° C. and 200 Ω·F or more at 150° C. under a strong electric field of 10 kV/mm. Therefore, the silicon oxide content preferably falls within a range of 0.2 to 5.0 mol as SiO
2
with respect to 100 mol of the primary component.
Additionally, the amount of alkali metal oxide contained in barium titanate as an impurity is preferably 0.02 wt. % or less, since dielectric constant decreases when the alkali metal oxide content is more than 0.02 wt. %, as in the case of Sample No. 16.
Example 2
In a manner similar to that in Example 1, four species of barium titanate (BaTiO
3
) shown in Table 1 and silicon oxide serving as an auxiliary component were prepared.
BaCO
3
and several oxides having purity of 99% or more were prepared. The oxides include Sc
2
O
3
, Y
2
O
3
, BaZrO
3
, MgO and MnO. BaCO
3
was used for adjusting the mole ratio of Ba/Ti in barium titanate. These powder materials and the silicon oxide serving as an auxiliary component were weighed to prepare the compositions shown in Table 4. The amount of added silicon oxide is represented as an amount by mol with respect to 100 mol of the primary component, [{BaO}
m
TiO
2
+αM
2
O
3
+γBaZrO
3
+gMgO+hMnO]. In a manner similar to that described in Example 1, laminated ceramic capacitors were prepared by use of the weighed mixtures. The outer size of each of the resultant laminated ceramic capacitors was the same as that in Example 1.
TABLE 4
|
|
Sample
Type of
α
SiO
2
|
No.
BaTiO
3
Sc
2
O
3
Y
2
O
3
Total α
γ
g
h
g + h
m
(mol)
|
|
*101
A
0
0.0008
0.0008
0.03
0.11
0.005
0.115
1.005
4
|
*102
A
0.02
0.05
0.07
0.03
0.06
0.06
0.12
1.005
3
|
*103
A
0.02
0.01
0.03
0
0.02
0.03
0.05
1.01
1.5
|
*104
A
0.02
0.01
0.03
0.08
0.02
0.04
0.06
1.01
1.5
|
*105
A
0.005
0.015
0.02
0.02
0.001
0.034
0.035
1.01
1.5
|
*106
A
0.01
0.02
0.03
0.03
0.125
0.005
0.13
1.01
4
|
*107
A
0.01
0.03
0.04
0.02
0.079
0.001
0.08
1.01
3
|
*108
A
0.01
0.02
0.03
0.02
0.005
0.125
0.13
1.01
2
|
*109
A
0.02
0.01
0.03
0.02
0.06
0.08
0.14
1.01
3
|
*110
A
0.01
0.02
0.03
0.03
0.03
0.02
0.05
0.99
1
|
*111
A
0.01
0.01
0.02
0.03
0.03
0.02
0.05
1
1
|
*112
A
0.01
0.01
0.02
0.02
0.01
0.03
0.04
1.04
4
|
*113
A
0.01
0.01
0.02
0.03
0.01
0.02
0.03
1.01
0
|
*114
A
0.02
0.01
0.03
0.02
0.005
0.045
0.05
1.01
0.1
|
*115
A
0.01
0.02
0.03
0.03
0.11
0.01
0.12
1.01
8
|
*116
D
0.02
0.01
0.03
0.03
0.03
0.03
0.06
1.01
2
|
117
B
0.01
0.01
0.02
0.03
0.01
0.02
0.03
1.005
1
|
118
C
0
0.02
0.02
0.02
0.02
0.015
0.035
1.01
1.5
|
119
A
0
0.001
0.001
0.02
0.12
0.002
0.122
1.015
4
|
120
A
0.01
0.04
0.05
0.03
0.01
0.12
0.13
1.01
3
|
121
A
0
0.01
0.01
0.005
0.02
0.01
0.03
1.01
1.5
|
122
A
0.02
0
0.02
0.04
0.02
0.02
0.04
1.01
1.5
|
123
A
0.01
0.02
0.03
0.06
0.02
0.03
0.05
1.005
1.5
|
124
A
0.01
0.01
0.02
0.02
0.03
0.02
0.05
1.035
5
|
125
A
0
0.02
0.02
0.03
0.005
0.025
0.03
1.015
0.2
|
126
A
0.01
0.05
0.06
0.03
0.01
0.1
0.11
1.01
2.5
|
127
A
0.02
0.02
0.04
0.03
0.01
0.04
0.05
1.01
1
|
128
A
0.01
0.02
0.02
0.02
0.02
0.05
0.07
1.01
2
|
|
Samples marked with * are beyond the scope of the present invention.
|
In a manner similar to that described in Example 1, the electric properties of the capacitors were measured. The results are shown in Table 5.
TABLE 5
|
|
DC bias
|
Rate of change in capacitance with
characteristic
|
Firing
Dielectric
temperature (%)
(%)
|
Sample
temperature
Dielectric
loss:
ΔC/C
20
ΔC/C
25
Maximum
ΔC/C
25
|
No.
(° C.)
constant
tan δ (%)
−25° C.
85° C.
−55° C.
125° C.
value
5 kV/mm
|
|
*101
1300
1720
0.8
5.6
−12.4
4.7
−17.1
19.9
−51
|
*102
1280
860
0.6
2
−7.3
4.3
−6.6
8.1
−13
|
*103
1280
1430
0.8
2.1
−7.9
4.3
−8.1
9
−36
|
*104
1300
1370
0.6
2.3
−14.8
5
−29.6
35.5
−26
|
*105
1280
1530
0.7
3.3
−14.1
4.2
−17.8
22.9
−42
|
*106
1360
1310
2.7
2.4
−8.4
4.2
−8.7
9.1
−27
|
*107
Not measurable because of semiconductivity
|
*108
1280
1250
0.8
3.4
−9
4.7
−18.7
25.2
−20
|
*109
1280
1360
2.6
3.6
−9.1
3.9
−9
9.8
−33
|
*110
Not measurable because of semiconductivity
|
*111
1300
1490
0.7
4
−8.9
4.8
−9.2
10.1
−40
|
*112
Not measurable because of poor sintering
|
*113
Not measurable because of poor sintering
|
*114
1360
1370
2.5
2.7
−8.5
3
−7.7
8.5
−29
|
*115
1300
1000
0.6
4.1
−14.4
4.3
−19
20.8
−15
|
*116
1300
1030
0.7
3.9
−9
4.1
−9.5
11
−13
|
117
1280
1530
0.6
2.6
−7.3
4.2
−8.3
8.7
−45
|
118
1300
1550
0.7
2.5
−7.7
4
−8.4
9
−42
|
119
1280
1600
0.6
2.4
−7.3
3.7
−8.6
8.9
−44
|
120
1280
1060
0.7
2.5
−8
4.3
−8.3
8.8
−16
|
121
1300
1580
0.7
2.8
−8
4
−8.3
8.9
−44
|
122
1300
1490
0.7
3.2
−7
4.4
−7.8
8.4
−40
|
123
1280
1430
0.6
3.1
−8.2
3.7
−8.4
9.1
−36
|
124
1300
1550
0.6
2.7
−7.8
4.6
−8
8.7
−43
|
125
1280
1570
0.7
2.4
−8.1
4
−8.6
9
−42
|
126
1300
1060
0.7
2.3
−8.2
4.1
−8.5
9
−16
|
127
1300
1330
0.7
2.4
−8.4
3.7
−8.7
8.9
−26
|
128
1300
1540
0.6
2.6
−7.3
4.2
−8.3
8.7
−43
|
|
Number of
|
defective
|
C × R (Ω · F)
Breakdown
capacitors in
|
Application
Application
Application
Application
voltage
humidity
|
Sample
of 315 V
of 945 V
of 315 V
of 945 V
(kV/mm)
resistance
Average
|
No.
25° C.
150° C.
AC
DC
test
life (h)
|
|
*101
5140
4880
220
210
12
14
0/72
900
|
*102
5040
4850
230
220
12
14
0/72
840
|
*103
3150
2210
160
120
13
15
0/72
850
|
*104
5180
4920
240
230
12
14
0/72
160
|
*105
3060
2910
120
110
13
14
0/72
820
|
*106
5150
4890
230
220
12
14
59/72
190
|
*107
Not measurable because of semiconductivity
|
*108
3130
2970
130
120
12
14
0/72
180
|
*109
5020
4770
250
240
12
14
16/72
140
|
*110
Not measurable because of semiconductivity
|
*111
3290
3130
150
140
10
12
0/72
100
|
*112
Not measurable because of poor sintering
|
*113
Not measurable because of poor sintering
|
*114
3140
2890
170
160
12
14
39/72
820
|
*115
3320
3160
170
160
12
14
0/72
830
|
*116
5110
3160
230
160
12
14
0/72
810
|
117
5060
4810
250
240
12
14
0/72
970
|
118
5150
4890
220
210
13
15
0/72
870
|
119
5060
4810
250
240
12
14
0/72
940
|
120
5220
4960
210
200
13
15
0/72
830
|
121
5190
4930
240
230
12
14
0/72
900
|
122
5310
5050
280
270
12
15
0/72
910
|
123
5230
4970
270
260
13
14
0/72
820
|
124
5240
4980
250
240
13
14
0/72
910
|
125
5090
4840
280
270
12
15
0/72
880
|
126
5240
4980
230
220
13
15
0/72
850
|
127
5170
4910
260
250
12
14
0/72
840
|
128
5050
4800
220
210
12
14
0/72
960
|
|
Samples marked with * are beyond the scope of the present invention.
|
As is clearly shown in Tables 4 and 5, the laminated ceramic capacitors of the present invention provide the following results: the rate of reduction in capacitance was −45% or less under application of a DC voltage of 5 kV/mm, dielectric loss was 1.0% or less and the rate of change in electrostatic capacity with temperature satisfied the B characteristics specified by JIS specifications within a range of −25° C. to +85° C., and satisfied the X7R characteristics specified by EIA specifications within a range of −55° C. to +125° C.
When the ceramic capacitor was used under a strong electric field of 10 kV/mm, insulation resistance represented by C×R product was as high as 5000 Ω·F or more at 25° C., and 200 Ω·F or more at 150° C. Breakdown voltage was as high as 12 kV/mm or more under application of AC voltage, and 14 kV/mm or more under application of DC voltage. In an accelerated test under application of 25 kV/mm at 150° C., the capacitor had a long life of 800 hours or longer, and could be fired at a relatively low temperature of 1300° C. or lower. There was little difference in electric properties between lots of capacitors, which are not shown in any tables.
Next will be described the reasons why the composition of the present invention is limited as described.
The primary component of the composition of the present invention is represented by {BaO}
m
TiO
2
+αM
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein M
2
O
3
is Sc
2
O
3
or Y
2
O
3
, and α, γ, g and h each represent a mole ratio. When the amount of M
2
O
3
represented by α is less than 0.001 as in the case of Sample No. 101, the temperature-dependent characteristics fail to satisfy the B and X7R characteristics. When α is more than 0.06 as in the case of Sample No. 102, the dielectric constant disadvantageously decreases to lower than 1000. Therefore, α preferably falls within a range of 0.001≦α≦0.06.
When the amount of BaZrO
3
represented by γ is zero as in the case of Sample No. 103, insulation resistance is low and voltage dependence of insulation resistance is disadvantageously high, as compared with samples including BaZrO
3
. When γ is more than 0.06 as in the case of Sample No. 104, the temperature-dependent characteristics fail to satisfy the B and X7R characteristics and the average life is disadvantageously short. Therefore, γ preferably falls within a range of 0.005≦γ≦0.06.
When the amount of MgO represented by g is 0.001 as in the case of Sample No. 105, insulation resistance is low, and temperature-dependent characteristics fail to satisfy B and X7R characteristics. When g is more than 0.12 as in the case of Sample No. 106, unfavorable results are obtained, such as high sintering temperature, dielectric loss of more than 2.0%, drastic increase in defective rate of capacitors in a humidity resistance test and short average life. Therefore, g preferably falls within a range of 0.001<g≦0.12.
When the MnO content represented by h is 0.001 as in the case of Sample No. 107, measurement is impossible because the capacitors for this sample No. exhibit a semi-conducting property. When h is more than 0.12 as in the case of Sample No. 108, temperature-dependent characteristics fail to satisfy the X7R characteristics, and insulation resistance is disadvantageously low and the average life is disadvantageously short. Therefore, h preferably falls within a range of 0.001<h≦0.12.
When the total amount of MgO and MnO represented by g+h is more than 0.13 as in the case of Sample No. 109, unfavorable results are obtained, such as high dielectric loss of 2.0% or more, short average life and increase in the defectives rate of capacitors in a humidity resistance test. Therefore, g+h is preferably 0.13 or less.
When the ratio of BaO/TiO
2
represented by m is less than 1.000 as in the case of Sample No. 110, measurement is impossible because the capacitors for this sample No. exhibit a semi-conducting property. When m is 1.000 as in the case of Sample No. 111, unfavorable results are obtained, such as low insulation resistance, low insulation breakdown under application of AC or DC voltage and short average life. When m is more than 1.035 as in the case of Sample No. 112, measurement is impossible because of poor sintering. Therefore, m preferably falls within a range of 1.000<m≦1.035.
When the SiO
2
content is zero as in the case of Sample No. 113, sintering is poor. When the SiO
2
content is less than 0.2 mol as in the case of Sample No. 114, insulation resistance decreases with increase in sintering temperature and the humidity resistance test produces a very high defectives rate of capacitors. When the SiO
2
content is more than 5.0 mol as in the case of Sample No. 115, dielectric constant decreases, the temperature-dependent characteristics fail to satisfy the X7R characteristics, and C×R fails to satisfy 5000 Ω·F or more at 25° C. and 200 Ω·F or more at 150° C. under a strong electric field of 10 kV/mm. Therefore, the amount of silicon oxide preferably falls within a range between 0.2 and 5.0 mol as SiO
2
with respect to 100 mol of the primary component.
Additionally, the amount of alkali metal oxide included in barium titanate as an impurity is preferably 0.02 wt. % or less, since dielectric constant decreases when the amount of alkali metal oxide is more than 0.02 wt. %, as in the case of Sample No. 116.
Example 3
In a manner similar to that described in Example 1, four species of barium titanate (BaTiO
3
) shown in Table 1 and silicon oxide serving as an auxiliary component were prepared.
BaCO
3
and several oxides having purity of 99% or more were prepared. The oxides include Sc
2
O
3
, Y
2
O
3
, Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, BaZrO
3
, MgO and MnO. BaCO
3
was used for adjusting the mole ratio of Ba/Ti in barium titanate. These powder materials and the silicon oxide serving as an auxiliary component were weighed to prepare the compositions shown in Tables 6 and 7. The amount of added silicon oxide is represented as an amount by mol with respect to 100 mol of the primary component, [{BaO}
m
TiO
2
+αM
2
O
3
+βR
2
O
3
+γBazrO
3
+gMgO+hMnO]. In a manner similar to that described in Example 1, laminated ceramic capacitors were prepared by use of the weighed mixtures. The outer size of each of the resultant laminated ceramic capacitors was the same as that in Example 1.
TABLE 6
|
|
{BaO}
m
•TiO
2
+ αM
2
O
3
+ βR
2
O
3
+ γBaZrO
3
+ gMgO + hMnO
|
Sample
Type of
α
β
SiO
2
|
No.
BaTiO
3
Sc
2
O
3
Y
s
O
3
Total α
Eu
2
O
3
Gd
2
O
3
Tb
2
O
3
Dy
2
O
3
Total β
α + β
γ
g
h
g + h
m
(mol)
|
|
*201
A
0
0.0008
0.0008
0
0.05
0
0
0.05
0.0508
0.02
0.05
0.07
0.12
1.005
2
|
*202
A
0.2
0.04
0.06
0
0
0.001
0
0.001
0.061
0.03
0.02
0.1
0.12
1.005
1
|
*203
A
0.005
0.015
0.02
0
0
0.0008
0
0.0008
0.0208
0.03
0.02
0.03
0.05
1.005
2
|
*204
A
0
0.001
0.001
0
0.03
0
0.025
0.055
0.056
0.03
0.03
0.09
0.12
1.01
2
|
*205
A
0.01
0.02
0.03
0.02
0
0
0.02
0.04
0.07
0.03
0.11
0.01
0.12
1.01
4
|
*206
A
0.01
0.01
0.02
0
0.02
0.02
0
0.04
0.06
0
0.07
0.05
0.12
1.01
1.5
|
*207
A
0
0.01
0.01
0
0
0
0.02
0.02
0.03
0.08
0.03
0.04
0.07
1.01
3
|
*208
A
0.02
0.01
0.03
0
0
0.01
0.01
0.02
0.05
0.02
0.001
0.069
0.07
1.01
1.5
|
*209
A
0.01
0
0.01
0.01
0
0
0
0.01
0.02
0.02
0.125
0.002
0.127
1.01
4
|
*210
A
0.01
0.01
0.02
0.01
0.01
0
0
0.02
0.04
0.02
0.079
0.001
0.08
1.01
1.5
|
*211
A
0.01
0
0.01
0
0.01
0
0.01
0.02
0.03
0.02
0.002
0.125
0.127
1.01
2
|
*212
A
0.02
0.01
0.03
0.02
0
0
0.01
0.03
0.06
0.03
0.06
0.08
0.14
1.01
3
|
*213
A
0.005
0.005
0.01
0
0.01
0.01
0
0.02
0.03
0.03
0.03
0.025
0.055
0.99
1
|
*214
A
0.01
0
0.01
0.01
0.005
0.005
0.01
0.03
0.04
0.04
0.04
0.03
0.07
1
1
|
*215
A
0.005
0.005
0.01
0
0
0.01
0
0.01
0.02
0.04
0.02
0.03
0.05
1.04
4
|
*216
A
0
0.01
0.01
0
0
0.01
0.01
0.02
0.03
0.01
0.01
0.01
0.02
1.01
0
|
*217
A
0.01
0
0.01
0
0.01
0.01
0.01
0.03
0.04
0.04
0.01
0.05
0.06
1.01
0.1
|
*218
A
0.03
0
0.03
0.01
0.02
0
0
0.03
0.06
0.03
0.11
0.01
0.12
1.005
8
|
*219
D
0
0.01
0.01
0
0.01
0.02
0
0.03
0.04
0.03
0.04
0.05
0.09
1.01
2
|
220
B
0.01
0.01
0.02
0
0
0.01
0
0.01
0.03
0.02
0.03
0.02
0.05
1.01
1.5
|
|
Samples marked with * are beyond the scope of the present invention.
|
TABLE 7
|
|
{BaO}
m
•TiO
2
+ αM
2
O
3
+ βR
2
O
3
+ γBaZrO
3
+ gMgO + hMnO
|
Sample
Type of
α
β
SiO
2
|
No.
BaTiO
3
Sc
2
O
3
Y
s
O
3
Total α
Eu
2
O
3
Gd
2
O
3
Tb
2
O
3
Dy
2
O
3
Total β
α + β
γ
g
h
g + h
m
(mol)
|
|
221
C
0
0.02
0.02
0
0
0
0.01
0.01
0.03
0.02
0.03
0.03
0.06
1.005
1.5
|
222
A
0
0.001
0.001
0.02
0
0.009
0
0.029
0.03
0.02
0.04
0.01
0.05
1.015
2
|
223
A
0.01
0.04
0.05
0
0.005
0
0
0.005
0.055
0.03
0.002
0.11
0.112
1.01
1.5
|
224
A
0.02
0.01
0.03
0
0
0
0.01
0.01
0.04
0.03
0.12
0.002
0.122
1.03
5
|
225
A
0
0.01
0.01
0
0.02
0.03
0
0.05
0.06
0.03
0.002
0.11
0.112
1.01
2
|
226
A
0.005
0.005
0.01
0
0
0
0.001
0.001
0.011
0.02
0.01
0.02
0.03
1.005
1
|
227
A
0.02
0.01
0.03
0
0.01
0.01
0
0.02
0.05
0.03
0.01
0.12
0.13
1.01
1.5
|
228
A
0
0.01
0.01
0
0.02
0
0
0.02
0.03
0.005
0.03
0.02
0.05
1.01
2
|
229
A
0.01
0.01
0.02
0
0.01
0.01
0
0.02
0.04
0.06
0.02
0.05
0.07
1.01
2
|
230
A
0.01
0.01
0.02
0
0
0.01
0.01
0.02
0.04
0.03
0.03
0.05
0.08
1.035
4
|
231
A
0.01
0.01
0.02
0
0
00.01
0.01
0.02
0.04
0.03
0.01
0.06
0.07
1.01
0.2
|
232
A
0
0.02
0.02
0
0
0
0.01
0.01
0.03
0.03
0.02
0.04
0.06
1.01
1.5
|
233
A
0.01
0.01
0.02
0.01
0
0.01
0
0.02
0.04
0.03
0.01
0.06
0.07
1.01
1.5
|
234
A
0
0.01
0.01
0.01
0.01
0
0
0.02
0.03
0.02
0.03
0.02
0.05
1.01
1.5
|
|
In a manner similar to that described in Example 1, the electric properties of the capacitors were measured. The results are shown in Tables 8 and 9.
|
TABLE 8
|
|
DC bias
|
Rate of change in capacitance with
characteristic
|
Firing
Dielectric
temperature (%)
(%)
|
Sample
temperature
Dielectric
loss:
ΔC/C
20
ΔC/C
25
Maximum
ΔC/C
25
|
No.
(° C.)
constant
tan δ (%)
−25° C.
85° C.
−55° C.
125° C.
value
5 kV/mm
|
|
*201
1300
1220
0.7
5.7
−11.9
6.5
−17.4
20.9
−20
|
*202
1300
950
0.6
2.2
−7.9
4.6
−7
8.8
−17
|
*203
1300
1560
0.6
3.1
−7.8
5.1
−6.7
8.4
−43
|
*204
1300
910
0.7
5.9
−13
7.4
−19.1
25.4
−13
|
*205
1280
970
2
2.2
−7.9
4.3
−7
8.4
−15
|
*206
1280
1060
0.7
1.8
−8.3
2.9
−7.6
9
−17
|
*207
1300
1450
0.8
2.3
−14.2
4.6
−31.4
36.1
−35
|
*208
1280
1270
0.8
2.1
−12.6
4.5
−16.4
21.4
−27
|
*209
1360
1540
2.6
2.4
−7.6
5.1
−7.4
8.4
−44
|
*210
Not measurable because of semiconductivity
|
*211
1280
1470
0.7
3.1
−8.4
5.2
−17.8
23.5
−39
|
*212
1280
930
2.1
2.2
−8.3
4.4
−8.6
8.8
−15
|
*213
Not measurable because of semiconductivity
|
*214
1300
1350
0.7
3.3
−8.5
5.2
−8.1
9.4
−31
|
*215
Not measurable because of poor sintering
|
*216
Not measurable because of poor sintering
|
*217
1360
1330
0.8
3.5
−9.3
4
−12.9
12.9
−26
|
*218
1300
950
0.8
3.2
−13.2
3.8
−28.5
28.5
−13
|
*219
1300
1150
0.7
2.3
−8.8
7.1
−8.2
9.4
−25
|
220
1280
1490
0.7
2.6
−8.4
6.1
−8.1
9.1
−41
|
|
Number of
|
defective
|
C × R (Ω · F)
Breakdown
capacitors in
|
Application
Application
Application
Application
voltage
humidity
|
Sample
of 315 V
of 945 V
of 315 V
of 945 V
(kV/mm)
resistance
Average
|
No.
25° C.
150° C.
AC
DC
test
life (h)
|
|
*201
5120
4870
230
220
12
14
0/72
880
|
*202
8510
8080
190
180
12
14
0/72
850
|
*203
3030
2880
130
120
13
14
0/72
890
|
*204
5070
4820
260
250
12
14
0/72
130
|
*205
5060
4810
250
240
13
14
39/72
170
|
*206
3130
2190
150
110
13
14
0/72
860
|
*207
5170
4910
250
240
12
14
0/72
170
|
*208
3080
2930
120
110
13
14
0/72
820
|
*209
5120
4870
240
230
12
14
43/72
110
|
*210
Not measurable because of semiconductivity
|
*211
3140
2980
140
130
12
14
0/72
140
|
*212
5070
4810
250
240
12
14
20/72
110
|
*213
Not measurable because of semiconductivity
|
*214
3190
3030
150
140
10
11
0/72
120
|
*215
Not measurable because of poor sintering
|
*216
Not measurable because of poor sintering
|
*217
3130
2970
180
170
12
14
38/72
800
|
*218
3280
3120
160
150
12
14
0/72
820
|
*219
5190
4930
290
280
12
14
0/72
870
|
220
5220
4960
220
210
12
14
0/72
900
|
|
TABLE 9
|
|
DC bias
|
Rate of change in capacitance with
characteristic
|
Firing
Dielectric
temperature (%)
(%)
|
Sample
temperature
Dielectric
loss:
ΔC/C
20
ΔC/C
25
Maximum
ΔC/C
25
|
No.
(° C.)
constant
tan δ (%)
−25° C.
85° C.
−55° C.
125° C.
value
5 kV/mm
|
|
221
1280
1450
0.6
1.9
−7.9
6.6
−8.1
8.7
−39
|
222
1280
1490
0.6
5.3
−7.1
6.6
−6.9
8.6
−40
|
223
1300
1070
0.6
2
−8.9
5.4
−8.4
9.3
−18
|
224
1280
1360
0.6
1.8
−8.4
5.7
−7.7
8.8
−30
|
225
1300
1090
0.7
2.2
−8.7
5.6
−8.2
9.1
−18
|
226
1300
1640
0.7
2
−7.6
6
−7.6
8.8
−45
|
227
1300
1070
0.7
2
−8.9
5.4
−8.4
9.3
−18
|
228
1280
1430
0.6
2.1
−8.1
5.4
−7.8
8.8
−35
|
229
1300
1360
0.6
2.4
−8
5.9
−7.7
8.1
−33
|
230
1300
1360
0.7
2.1
−8
5.9
−7.9
8.4
−31
|
231
1300
1340
0.6
1.9
−8.1
6
−7.8
8.6
−31
|
232
1280
1440
0.6
2.4
−7.9
6.9
−7.8
8.7
−39
|
233
1300
1430
0.6
2.1
−8
6.4
−7.6
9.1
−37
|
234
1300
1420
0.7
3.1
−7.8
6.8
−7.2
8.7
−37
|
|
Number of
|
defective
|
C × R (Ω · F)
Breakdown
capacitors in
|
Application
Application
Application
Application
voltage
humidity
|
Sample
of 315 V
of 945 V
of 315 V
of 945 V
(kV/mm)
resistance
Average
|
No.
25° C.
150° C.
AC
DC
test
life (h)
|
|
221
5230
4970
270
260
12
14
0/72
900
|
222
5080
4830
260
250
12
15
0/72
910
|
223
5210
4950
230
220
12
15
0/72
940
|
224
5290
5030
300
290
12
15
0/72
880
|
225
5210
4950
230
220
13
15
0/72
940
|
226
5220
4960
240
230
12
14
0/72
830
|
227
5210
4950
230
220
12
15
0/72
940
|
228
5070
4820
290
280
12
15
0/72
860
|
229
5090
4840
210
200
12
14
0/72
840
|
230
5370
5100
260
250
12
14
0/72
890
|
231
5080
4830
260
250
12
14
0/72
900
|
232
5240
4980
280
270
12
14
0/72
850
|
233
5270
5010
270
260
12
14
0/72
930
|
234
5280
5020
270
260
12
14
0/72
840
|
|
As is clearly shown in Tables 8 and 9, the laminated ceramic capacitors of the present invention provide the following results: the rate of reduction in capacitance is −45% or less under application of a DC voltage of 5 kV/mm, dielectric loss is 1.0% or less, and the rate of change in electrostatic capacity with temperature satisfies the B characteristics specified by JIS specifications within a range of −25° C. to +85° C., and satisfies the X7R characteristics specified by EIA specifications within a range of −55° C. to +125° C.
When the ceramic capacitor was used under a strong electric field of 10 kV/mm, insulation resistance represented by C×R was as high as 5000 Ω·F or more at 25° C., and 200 Ω·F or more at 150° C. Breakdown voltage was as high as 12 kV/mm or more under application of AC voltage, and 14 kV/mm or more under application of DC voltage. In an accelerated test under application of 25 kV/mm at 150° C., the capacitor had a long life of 800 hours or longer and could be fired at a relatively low temperature of 1300° C. or lower. There was little difference in electric properties between lots of capacitors, which are not shown in any tables.
Next will be described the reasons why the composition of the present invention is limited as described.
The primary component of the composition of the present invention is represented by {BaO}
m
TiO
2
+αM
2
O
3
+βR
2
O
3
+γBaZrO
3
+gMgO+hMnO wherein M
2
O
3
is Sc
2
O
3
or Y
2
O
3
, R
2
O
3
is selected from the group consisting of Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, and Dy
2
O
3
, and α, β, γ, g, and h each represent a mole ratio.
When the amount of M
2
O
3
represented by α is less than 0.001 as in the case of Sample No. 201, the temperature dependent characteristics fail to satisfy the B and X7R characteristics, whereas when αis more than 0.05 as in the case of Sample No. 202, the dielectric constant disadvantageously decreases to lower than 1000. Therefore, αpreferably falls within a range of 0.001≦α≦0.05.
When the amount of R
2
O
3
represented by β is less than 0.001 as in the case of Sample No. 203, insulation resistance is low and C×R (Ω·F) disadvantageously decreases. When β is more than 0.05 as in the case of Sample No. 204, the temperature-dependent characteristics fail to satisfy the B and X7R characteristics. Therefore, β preferably falls within a range of 0.001≦β≦0.05.
When the total amount of M
2
O
3
and R
2
O
3
represented by α+β is more than 0.06 as in the case of Sample No. 205, unfavorable results are obtained, such as high dielectric loss of 2.0% or more, short average life and an increase in defective of capacitors in the humidity resistance test. Therefore, α+β is preferably 0.06 or less.
When the BaZrO
3
content represented by γ is zero as in the case of Sample No. 206, insulation resistance is low and temperature dependence of insulation resistance is disadvantageously higher than that of a system having BaZrO
3
. When γ is more than 0.06 as in the case of Sample No. 207, the temperature-dependent characteristics fail to satisfy the B and X7R characteristics and the average life is disadvantageously short. Therefore, γ is preferably within a range of 0.005≦γ≦0.06.
When the amount of MgO represented by g is 0.001 as in the case of Sample No. 208, insulation resistance is low, and the temperature-dependent characteristics disadvantageously fail to satisfy both B and X7R. When g is more than 0.12 as in the case of Sample No. 209, unfavorable results are obtained, such as high sintering temperature, high dielectric loss of more than 2.0%, drastic increase in defective capacitors in the humidity resistance test and short average life. Therefore, g preferably falls within a range of 0.001<γ≦0.12.
When the amount of MnO represented by h is 0.001 as in the case of Sample No. 210, measurement is impossible because the capacitors for this sample No. exhibit a semi-conducting property. When h is more than 0.12 as in the case of Sample No. 211, the temperature-dependent characteristics disadvantageously fail to satisfy the X7R characteristics, insulation resistance is low and the average life is short. Therefore, h preferably falls within a range of 0.001<h≦0.12.
When the total amount of MgO and MnO represented by g+h is more than 0.13 as in the case of Sample No. 212, unfavorable results are obtained, such as high dielectric loss of 2.0% or more, short average life, and increase in defective capacitors in the humidity resistance test. Therefore, g+h is preferably 0.13 or less.
When the ratio of BaO/TiO
2
represented by m is less than 1.000 as in the case of Sample No. 213, measurement is impossible because the capacitors for this sample exhibit a semi-conducting property. When m is 1.000 as in the case of Sample No. 214, unfavorable results are obtained, such as low insulation resistance, low insulation breakdown voltage under application of AC or DC voltage and short average life. When m is more than 1.035 as in the case of Sample No. 215, the measurement is impossible because of poor sintering. Therefore, m preferably falls within a range of 1.000<m≦1.035.
When the SiO
2
content is zero as in the case of Sample No. 216, insufficient sintering results. When the SiO
2
content is less than 0.2 mol as in the case of Sample No. 217, insulation resistance decreases with the increase of sintering temperature, and the rate of defective capacitors is considerably high in the humidity resistance test. When the SiO
2
content is more than 5.0 mol as in the case of Sample No. 218, dielectric constant decreases, the temperature-dependent characteristic of capacitance fails to satisfy the XR7 characteristic, and C×R fails to satisfy 5000 Ω·F or more at 25° C. and 200 Ω·F or more at 150° C. under a strong electric field of 10 kV/mm. Therefore, the silicon oxide content is preferably in the range between 0.2 and 5.0 mol as SiO
2
with respect to 100 mol of the primary component.
The alkali metal oxide contained in barium titanate as an impurity is limited to 0.02 wt. % or less. This is because dielectric constant decreases when the alkali metal oxide content is in excess of 0.02 wt. % as in the case of Sample No. 219.
In the above-described Examples, a barium titanate powder produced through an oxalic acid method was used. However, barium titanate is not limited only to the above-produced barium titanate. Barium titanate powder produced by use of the alkoxide method or hydrothermal synthesis method may be used. Use of such barium titanate powders may produce laminated ceramic capacitors having properties which are superior to those of capacitors described in the above Examples.
Oxide powders such as Sc
2
O
3
, Y
2
O
3
, Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, Ho
2
O
3
, Er
2
O
3
, Tm
2
O
3
, Yb
2
O
3
, MgO, MnO and BaZrO
3
were used as starting materials; however, the present invention is not limited only to these materials. Solutions of alkoxides or organic metals may be used so as to produce capacitors of the same properties, so long as the dielectric ceramic layer within the scope of the present invention is produced.
In the present invention, although there are employed specific oxide powders such as Sc
2
O
3
, Y
2
O
3
, Eu
2
O
3
, Gd
2
O
3
, Tb
2
O
3
, Dy
2
O
3
, Ho
2
O
3
, Er
2
O
3
, Tm
2
O
3
, Yb
2
O
3
, MgO, MnO and BaZrO
3
, the present invention is not limited by these species. That is, so long as the dielectric ceramic layer which falls within the scope of the present invention is formed, use of a solution of an alkoxide or organometallics does not impede the characteristics of the capacitors of the present invention.
As described hereinabove, even when sintered in a reducing atmosphere, the dielectric ceramic composition according to the present invention is neither reduced nor transformed to have semiconductivity. Moreover, the composition can be sintered at a relatively low temperature of 1300° C. or less.
Therefore, use of the dielectric ceramic composition according to the present invention as a dielectric ceramic layer in the fabrication of laminated ceramic capacitors allows employment, as electrode material, of a base metal such as nickel or nickel alloy, leading to reduction in production cost of laminated ceramic capacitors.
In use, the laminated ceramic capacitor making use of the dielectric ceramic composition of the invention exhibits excellent characteristics, particularly when it is used in a strong electric field of 10 kV/mm, where conventional laminated ceramic capacitors, which includes nickel or nickel alloy as internal electrodes, cannot secure reliability due to low insulation resistance. That is, the mentioned excellent characteristics of the laminated ceramic capacitor of the present invention include the following: high insulation resistance at room temperature as expressed by C×R of (5000 Ω·F) and 150° C. (200 Ω·F); insulation resistance being less dependent on voltage; the absolute value of rate of reduction in capacitance being 45% or less under application of a DC voltage of 5 kV/mm; high dielectric strength; temperature-dependent characteristics of electrostatic capacity satisfy the B characteristic specified by JIS specifications and the X7R characteristic specified by EIA specifications; and weather resistance as proven in a high temperature test and high humidity test performed under DC 25 kV/mm at 150° C.
Claims
- 1. A dielectric ceramic composition which comprises a primary component and an auxiliary component;the primary component comprising barium titanate having an alkali metal oxide content of 0.02 wt % or less, barium zirconate, magnesium oxide and manganese oxide, and is represented by the formula: {BaO}mTiO2+αM2O3+βR2O3+γBaZrO3+gMgO+hMnO wherein M2O3 is at least one of Sc2O3 or Y2O3; R2O3 is at least one member selected from the group consisting of Eu2O3, Gd2O3, Tb2O3. Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3, α, β, γ, g or h each represent a mole ratio; and α is 0 or 0.001≦α≦0.06; β is 0 or 0.001≦β≦0.06; 0.001≦γ≦0.06; 0.001<g≦0.12; 0.001<h≦0.12; α+β≦0.06 g+h≦0.13; and 1.000<m≦1.035, provided that when α has a positive value, R2O3 is at least one member selected from the group consisting of Eu2O3, Gd2O3, Tb2O3 and Dy2O3 and when β has a positive value, 0.005≦γ; andthe auxiliary component being silicon oxide in an amount of 0.2-5.0 mol calculated as SiO2 with respect to 100 mols of the primary component.
- 2. A laminated ceramic capacitor comprising a plurality of dielectric ceramic layers, internal electrodes between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, wherein the dielectric ceramic layers comprise the dielectric ceramic composition of claim 1.
- 3. A laminated ceramic capacitor according to claim 2 wherein the internal electrodes are nickel or a nickel alloy.
- 4. A laminated ceramic capacitor according to claim 3, wherein the external electrodes comprise a sintered layer of conductive metal powder or of glass frit-containing conductive metal powder.
- 5. A laminated ceramic capacitor according to claim 4, wherein the external electrodes comprise a first sintered layer of conductive metal powder or glass frit-containing conductive metal powder; and a second layer which is a plating layer provided thereon.
- 6. A dielectric ceramic composition according to claim 1 wherein the primary component is represented by the formula:{BaO}mTiO2+βR2O3+γBaZrO3+gMgO+hMnO wherein R2O3 is at least one member selected from the group consisting of Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3; 0.001≦β≦0.06; and 0.005≦γ≦0.06.
- 7. A laminated ceramic capacitor comprising a plurality of dielectric ceramic layers, internal electrodes between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, wherein the dielectric ceramic layers comprise the dielectric ceramic composition of claim 6.
- 8. A laminated ceramic capacitor according to claim 7 wherein the internal electrodes are nickel or a nickel alloy.
- 9. A laminated ceramic capacitor according to claim 8, wherein the external electrodes comprise a sintered layer of conductive metal powder or of glass frit-containing conductive metal powder.
- 10. A laminated ceramic capacitor according to claim 8, wherein the external electrodes comprise a first sintered layer of conductive metal powder or glass frit-containing conductive metal powder; and a second layer which is a plating layer provided thereon.
- 11. A dielectric ceramic composition according to claim 1 wherein the primary component is represented by the formula:{BaO}mTiO2+αM2O3+γBaZrO3+gMgO+hMnO wherein 0.001≦α≦0.06; and 0.001≦γ≦0.06.
- 12. A laminated ceramic capacitor comprising a plurality of dielectric ceramic layers, internal electrodes between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, wherein the dielectric ceramic layers comprise the dielectric ceramic composition of claim 11.
- 13. A laminated ceramic capacitor according to claim 9, wherein the external electrodes comprise a first sintered layer of conductive metal powder or glass frit-containing conductive metal powder; and a second layer which is a plating layer provided thereon.
- 14. A laminated ceramic capacitor according to claim 12 wherein the internal electrodes are nickel or a nickel alloy.
- 15. A laminated ceramic capacitor according to claim 14, wherein the external electrodes comprise a sintered layer of conductive metal powder or of glass frit-containing conductive metal powder.
- 16. A dielectric ceramic composition according to claim 1 wherein the primary component is represented by the formula:{BaO}mTiO2+αM2O3+βR2O3+γBaZrO3+gMgO+hMnO wherein R2O3 is at least one member selected from the group consisting of Eu2O3, Gd2O3, Tb2O3 and Dy2O3, 0.001≦α≦0.05; 0.001≦β≦0.05; and 0.005≦γ≦0.06.
- 17. A laminated ceramic capacitor comprising a plurality of dielectric ceramic layers, internal electrodes between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, wherein the dielectric ceramic layers comprise the dielectric ceramic composition of claim 16.
- 18. A laminated ceramic capacitor according to claim 17 wherein the internal electrodes are nickel or a nickel alloy.
- 19. A laminated ceramic capacitor according to claim 18, wherein the external electrodes comprise a sintered layer of conductive metal powder or of glass frit-containing conductive metal powder.
- 20. A laminated ceramic capacitor according to claim 18, wherein the external electrodes comprise a first sintered layer of conductive metal powder or glass frit-containing conductive metal powder; and a second layer which is a plating layer provided thereon.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-128625 |
May 1998 |
JP |
|
US Referenced Citations (9)
Foreign Referenced Citations (3)
Number |
Date |
Country |
073755A1 |
Oct 1996 |
EP |
0785561A2 |
Jul 1997 |
EP |
0893419AL |
Jan 1999 |
EP |