Dielectric ceramic compositions

Abstract

A dielectric ceramic composition consisting essentially of:PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3wherein x+y+z=1, which allows low-temperature sintering and has a high dielectric constant, a low dielectric loss and a high specific resistivity.

Description

FIELD OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to dielectric ceramic compositions capable of sintering at low-temperature, exhibiting a high dielectric constant, low temperature coefficient of the dielectric constant and low dielectric loss, and being suitable for use in ceramic capacitors. 2. Description of the Related Art

As promising ceramic compositions for the above-mentioned purpose, those essentially consisting of BaTiO.sub.3 have been widely used as substance of high dielectric constant. The dielectric constant of this substance has a relatively high temperature coefficient of the dielectric constant, while in general, a dielectric substance which exhibits a low temperature coefficient of the dielectric constant has a relatively low dielectric constant.

The temperature coefficient of a ceramic capacitor is established or defined by JIS (Japanese Industrial Standard) or EIA (U.S. Electronics Industries Association) Standard. For example, the temperature coefficient of a dielectric constant adaptable to YF rating of JIS, which is approximately equivalent to Y5 V rating of EIA Standard, means that the temperature coefficient varies within a range of +22 to -82% for operating range of -30.degree. C. to 85.degree. C. A dielectric material which exhibits a dielectric constant of 10,000, is adaptable to YF or Y5 V. However, BaTiO.sub.3 system ceramics must be sintered at a very high temperature in the range of 1300.degree. C. to 1400.degree. C., so that where they are used as a dielectric substance of multilayer ceramic capacitors, expensive metals such as platinum or palladium which can stand such high sintering temperature must be used as internal electrodes of the capacitors, thereby obstructing cost reduction. Therefor there has still been a demand for dielectric ceramic materials which can be sintered at a temperature as low as below 1100.degree. C. for enabling the use of relatively cheap metal such as silver-30% palladium for the internal electrodes.

U.S. Pat. No. 4,078,938 discloses binary system ceramic compositions of Pb(Fe.sub.2/3 Nb.sub.1/3)O.sub.3 -Pb(Fe.sub.1/2 W.sub.1/2)O.sub.3 which can be sintered at a temperature as low as below 1000.degree. C., and which exhibit a high dielectric constant of 20,000. However, the resultant ceramics have a relatively low specific resistivity.

U.S. Pat. No. 4,265,668 discloses binary system ceramic composition PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3, which exhibit a high dielectric constant of 20,000.

However, the ceramic compositions of this binary system must be sintered at a temperature range of 1100.degree. C. to 1150.degree. C.

U.S. Pat. No. 4,450,240 discloses ternary system ceramic compositions of PbTiO.sub.3 -Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Mg.sub.1/2 W.sub.1/2)O.sub.3, which can be sintered at a temperature range of 900.degree. C. to 1050.degree. C. and exhibit a high electrical resistivity. However, the ceramics have a dielectric constant under 15,000.

SUMMARY AND OBJECT OF THE INVENTION

The object of the present invention is to provide a dielectric ceramic composition which can be sintered at a temperature as low as below 1100.degree. C., and exhibits high dielectric constant and a high specific resistivity.

To attain the object, a ceramic composition of the present invention is a dielectric ceramic composition essentially comprising a substance represented by the formula.

PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 wherein x+y+z=1.00.

Other mode of the present invention contains MnO.sub.2, Cr.sub.2 O.sub.3, CoO And MoO.sub.3 as an additive.

Still other mode of the invention contains Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3.Pb(Mn.sub.1/2 Sb.sub.2/3)O.sub.3 as an additive.

These novel composition of the present invention can be sintered at a temperature in the range from 900.degree. C. to 1100.degree. C., and have a high dielectric constant up to 8,000, and low temperature coefficient of the dielectric constant which meet the YF rating of JIS or Y5 V rating of EIA standard, and further it has a high specific resistivity.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing is a composition diagram of PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 ternary system, wherein the polygon ABCDE shows a range of composition of the ceramic composition in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The composition herein may be prepared in accordance with various well-known ceramic procedures.

EXAMPLE 1

The starting materials, viz. lead oxide (PbO), titanium oxide (TiO.sub.2), niobium oxide(Nb.sub.2 O.sub.5), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO.sub.3), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range of 750.degree. C. to 880.degree. C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm.sup.2. After buring out the binder at about 700.degree. C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900.degree. C. to 1100.degree. C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 1. The dielectric constant (.epsilon.) and the dielectric loss (tan .delta.) were measured at a frequency of 1 KHz and a voltage of 1 V at 20.degree. C. The temperature coefficients of the dielectric constant were obtained by measuring the dielectric constants at temperatures in the range of -25.degree. C. to 85.degree. C. and then calculations are made with reference to the dielectric constant at 20.degree. C.

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20.degree. C. under application of a D.C. voltage of 1000 V.

From TABLE 1 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing provide a

TABLE 1__________________________________________________________________________ Sintering tan .delta. Change of SpecificComposition temperature .epsilon. 20.degree. C. .epsilon. (%) resistivityNo. x y z (.degree.C.) 20.degree. C. (.times. 10.sup.-4) (-25.degree. C.) (+85.degree. C.) (.OMEGA. .multidot. cm)__________________________________________________________________________1 0.025 0.950 0.025 1090 10780 400 -5.4 -34.0 6.0 .times. 10.sup.12 2* 0.070 0.930 0.000 1150 21040 460 -54.6 -57.4 4.5 .times. 10.sup.113 0.125 0.850 0.025 1090 17730 500 -66.0 -28.1 2.0 .times. 10.sup.13 4* 0.350 0.600 0.050 1100 3200 640 -12.5 +128.2 8.0 .times. 10.sup.125 0.375 0.450 0.175 980 10210 500 -74.3 -11.6 5.0 .times. 10.sup.126 0.200 0.700 0.100 1000 21350 410 -60.0 -54.0 1.0 .times. 10.sup.137 0.250 0.550 0.200 980 12110 90 -12.0 -55.0 8.0 .times. 10.sup.128 0.200 0.550 0.250 900 9850 45 -8.1 -60.3 2.5 .times. 10.sup.12 9* 0.100 0.600 0.300 900 4930 40 +121.2 -45.0 1.4 .times. 10.sup.1210 0.025 0.900 0.075 1030 11450 50 -13.3 -61.2 1.5 .times. 10.sup.1311* 0.000 0.930 0.070 1030 9660 50 -4.3 -89.6 1.2 .times. 10.sup.1312* 0.400 0.300 0.300 900 8760 102 -12.6 -45.3 1.0 .times. 10.sup.12__________________________________________________________________________ Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 Note 2: Compositions of the Nos. with an asterisk (*) are outside the scope of the present invention. high dielectric constant (.epsilon.= 9850-21350), high specific resistivity, low dielectric loss (tan .delta..ltoreq.500.times.10), low temperature coefficient of the dielectric constant which is adaptable to YF ranges rating of JIS and Y5 V rating of EIA Standard, and can be sintered below 1100.degree. C., for which the points A, B, C, D and E of FIG. 1 are represented by the values of x, y and z as shown in TABLE 2.

The reasons for the limitations of values in TABLE 2 are as follows.

In case of the composition wherein proportions of z is smaller than 0.025 such as sample No. 2, the sintering temperature is higher than 1100a.degree. C. Such compositions, which lie outside of line BC, DE and EA of the polygon ABCDE in the ternary system composition diagram as samples No. 4, 9 and 11, exhibit high temperature coefficients of dielectric constant. Such composition, which lies outside of line CD of the polygon ABCDE in the ternary system composition diagram, as sample No. 12 exhibits a dielectric constant which is lower than 9500.

EXAMPLE 2

The starting materials, viz. lead oxide(PbO), titanium oxide(TiO.sub.2), niobium oxide(Nb.sub.2 O.sub.5), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO.sub.3), manganese oxide(MnO.sub.2), cromium oxide(Cr.sub.2 O.sub.3), cobalt

TABLE 2______________________________________x y z______________________________________A 0.025 0.950 0.025B 0.125 0.850 0.025C 0.375 0.450 0.175D 0.200 0.550 0.250E 0.025 0.900 0.075______________________________________ oxide(CoO) and molybdenum oxide(MoO.sub.3), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750.degree. C. to 880.degree. C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm.sup.2. After buring out the binder at about 700.degree. C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900.degree. C. to 1100.degree. C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 3. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20.degree. C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25.degree. C. to 85.degree. C. and calculated with reference to the dielectric constant at 20.degree. C.

The sintering temperature is selected as the

TABLE 3__________________________________________________________________________ Sintering Specific Additive tempera- tan .delta. Change of resistivityComposition element ture .epsilon. 20.degree. C. .epsilon. (%) tivityNo. x y z wt % (.degree.C.) 20.degree. C. (.times. 10.sup.-4) (-25.degree. C.) (+85.degree. C.) (.OMEGA. .multidot. cm)__________________________________________________________________________ 1# 0.100 0.800 0.100 -- -- 1050 13930 310 +8.4 -54.1 1.2 .times. 10.sup.13 2 0.100 0.800 0.100 MnO.sub.2 0.05 1050 12230 122 +7.3 -48.3 1.2 .times. 10.sup.13 3 0.100 0.800 0.100 MnO.sub.2 0.20 1040 12100 63 +4.1 -43.0 1.4 .times. 10.sup.13 4* 0.100 0.800 0.100 MnO.sub.2 1.00 1010 5440 210 +5.1 -21.3 2.0 .times. 10.sup.12 5* 0.100 0.800 0.100 Cr.sub.2 O.sub.3 0.01 1040 13320 250 +8.1 -54.0 1.1 .times. 10.sup. 13 6 0.100 0.800 0.100 Cr.sub.2 O.sub.3 0.03 1030 13030 170 +5.1 -45.3 1.0 .times. 10.sup.13 7 0.100 0.800 0.100 Cr.sub.2 O.sub.3 0.15 1030 12420 102 +4.1 -45.4 7.5 .times. 10.sup.12 8* 0.100 0.800 0.100 Cr.sub.2 O.sub.3 0.70 1000 11450 340 +7.1 -21.9 2.5 .times. 10.sup.11 9* 0.100 0.800 0.100 CoO 0.02 1050 12980 280 +7.5 -49.3 1.0 .times. 10.sup.1310 0.100 0.800 0.100 CoO 0.40 1010 11390 175 +4.3 -40.6 1.0 .times. 10.sup.1311* 0.100 0.800 0.100 CoO 0.90 1000 5480 100 +12.5 -21.8 3.5 .times. 10.sup.1112* 0.100 0.800 0.100 MoO.sub.3 0.01 1050 13640 300 +8.0 -54.1 1.1 .times. 10.sup.1313 0.100 0.800 0.100 MoO.sub.3 0.40 1000 10960 180 +12.5 -43.7 8.5 .times. 10.sup.1214* 0.100 0.800 0.100 MoO.sub.3 0.90 960 6490 250 +13.2 -31.7 8.0 .times. 10.sup.1115 0.100 0.800 0.100 MnO.sub.2 0.10 CoO 0.05 1030 13340 100 +6.3 - 51.0 1.0 .times. 10.sup.1316# 0.200 0.700 0.100 -- -- 1000 21350 410 -6.3 -54.0 1.0 .times. 10.sup.1317* 0.200 0.700 0.100 MnO.sub.2 0.01 1000 21000 400 -6.2 -53.3 1.1 .times. 10.sup.1318 0.200 0.700 0.100 MnO.sub.2 0.03 1000 20000 200 -6.0 -51.4 1.5 .times. 10.sup.1319 0.200 0.700 0.100 MnO.sub.2 0.10 1000 19050 145 -0.4 -49.3 1.2 .times. 10.sup.1320 0.200 0.700 0.100 MnO.sub.2 0.60 1000 8430 73 +1.5 -39.3 5.0 .times. 10.sup.1221* 0.200 0.700 0.100 MnO.sub.2 1.00 980 5430 150 +7.8 -21.3 8.0 .times. 10.sup.1122* 0.200 0.700 0.100 Cr.sub.2 O.sub.3 0.02 1000 20640 315 -5.3 -51.3 1.4 .times. 10.sup.1323 0.200 0.700 0.100 Cr.sub.2 O.sub.3 0.30 950 14350 183 +9.3 -41.7 1.4 .times. 10.sup.1324* 0.200 0.700 0.100 Cr.sub.2 O.sub.3 0.70 900 11430 235 +15.3 -30.8 7.0 .times. 10.sup.1125* 0.200 0.700 0.100 CoO 0.01 1000 21430 315 -8.3 - 53.2 1.1 .times. 10.sup.1326 0.200 0.700 0.100 CoO 0.25 980 20180 175 -5.4 -51.3 1.0 .times. 10.sup.1327* 0.200 0.700 0.100 CoO 0.80 960 18930 220 -4.3 -50.6 3.0 .times. 10.sup.1128* 0.200 0.700 0.100 MoO.sub.3 0.01 980 20740 325 -6.0 -53.1 8.5 .times. 10.sup.1329 0.200 0.700 0.100 MoO.sub.3 0.40 950 16340 163 +3.1 -50.4 1.1 .times. 10.sup.1230* 0.200 0.700 0.100 MoO.sub.3 1.00 910 13320 230 +5.1 -48.3 4.0 .times. 10.sup.1131# 0.250 0.550 0.200 -- -- 980 12110 90 +4.4 -55.0 8.0 .times. 10.sup.1232 0.250 0.550 0.200 MnO.sub.2 0.08 970 10940 32 +3.2 -48.3 8.5 .times. 10.sup.1233 0.250 0.550 0.200 MnO.sub.2 0.40 950 8460 21 +0.3 -40.3 8.0 .times. 10.sup.1134* 0.250 0.550 0.200 MnO.sub.2 0.80 940 5540 83 -0.9 -31.3 1.0 .times. 10.sup.1135* 0.250 0.550 0.200 Cr.sub.2 O.sub.3 0.01 980 12330 87 +4.4 -55.3 8.0 .times. 10.sup.1236 0.250 0.550 0.200 Cr.sub.2 O.sub.3 0.03 980 12120 74 +4.0 -51.3 1.0 .times. 10.sup.1337 0.250 0.550 0.200 Cr.sub.2 O.sub.3 0.15 970 10770 40 +3.1 -43.3 1.3 .times. 10.sup.1338 0.250 0.550 0.200 Cr.sub.2 O.sub.3 0.50 950 8960 85 +1.0 -38.8 4.5 .times. 10.sup.1239* 0.250 0.550 0.200 Cr.sub.2 O.sub.3 1.00 930 5140 250 -3.5 -31.5 2.0 .times. 10.sup.1140 0.250 0.550 0.200 CoO 0.30 960 11540 174 -3.1 -42.3 8.0 .times. 10.sup.1241 0.250 0.550 0.200 CoO 0.50 960 10430 184 -6.3 -38.4 9.0 .times. 10.sup.1142* 0.250 0.550 0.200 CoO 0.80 970 9440 230 -7.4 -36.5 1.5 .times. 10.sup.1043* 0.250 0.550 0.200 MoO.sub.3 0.02 980 11340 210 +3.1 -53.2 8.5 .times. 10.sup.1244 0.250 0.550 0.200 MoO.sub.3 0.15 960 10420 152 +7.3 -48.1 1.2 .times. 10.sup.1245* 0.250 0.550 0.200 MoO.sub.3 0.80 960 5110 135 +4.3 -31.2 7.0 .times. 10.sup.11__________________________________________________________________________ Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 Note 2: Compositions of the Nos. with asterisk (*) are outside the scope of the present invention, with sharp (#) are included in the claim 1. temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20.degree. C. under application of a D.C. voltage of 1000 V.

From TABLE 3 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Mn, Cr, Co and Mo in an amount in total equivalent 0.03 to 0.06 weight % of respective oxides (MnO.sub.2, Cr.sub.2 O.sub.3, CoO and MoO.sub.3) exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant even with low sintering temperature.

The reasons for the limitations in TABLE 3 are as follows.

If content of MoO.sub.2, Cr.sub.2 O.sub.3, CoO and MoO.sub.3 in total is smaller than 0.03 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 0.60 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

EXAMPLE 3

The starting materials, viz. lead oxide(PbO), titanium oxide(TiO.sub.2), niobium oxide(Nb.sub.2 O.sub.5), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO.sub.3), manganese oxide(MnO.sub.2) and antimony oxide(Sb.sub.2 O.sub.5), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750.degree. C. to 880a.degree. C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm.sup.2. After buring out the binder at about 700.degree. C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900.degree. C. ato 1100.degree. C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 4. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20.degree. C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25.degree. C. to 85.degree. C. and calculated with reference to the dielectric constant at 20.degree. C.

TABLE 4__________________________________________________________________________ Sintering Specific Additive tempera- tan .delta. Change of resistivityComposition element ture .epsilon. 20.degree. C. .epsilon. (%) tivityNo. x y z wt % (.degree.C.) 20.degree. C. (.times. 10.sup.-4) (-25.degree. C.) (+85.degree. C.) (.OMEGA. .multidot. cm)__________________________________________________________________________ 1# 0.100 0.800 0.100 -- -- 1050 13930 310 +8.4 -54.1 1.2 .times. 10.sup.13 2* 0.100 0.800 0.100 MnNb 0.20 1040 13010 220 +3.1 -52.3 1.0 .times. 10.sup.13 3 0.100 0.800 0.100 MnNb 0.80 1020 12150 107 +2.1 -50.1 8.0 .times. 10.sup.12 4 0.100 0.800 0.100 MnNb 2.00 1000 10840 102 -2.1 -48.1 8.5 .times. 10.sup.11 5* 0.100 0.800 0.100 MnNb 3.00 1000 9410 215 -2.1 -38.2 2.5 .times. 10.sup.11 6* 0.100 0.800 0.100 MnW 0.10 1040 13390 280 +7.1 -53.2 1.1 .times. 10.sup.13 7 0.100 0.800 0.100 MnW 0.50 1030 12840 147 +5.1 -50.4 8.0 .times. 10.sup.12 8 0.100 0.800 0.100 MnW 1.00 1000 10430 78 +2.1 -46.3 8.0 .times. 10.sup.12 9 0.100 0.800 0.100 MnW 2.50 960 6440 109 -3.5 -38.4 2.5 .times. 10.sup.1210* 0.100 0.800 0.100 MnW 4.00 940 3180 215 -5.3 -30.6 7.5 .times. 10.sup.1111* 0.100 0.800 0.100 MnSb 0.20 1040 13380 254 +7.1 -53.1 1.4 .times. 10.sup.1312 0.100 0.800 0.100 MnSb 0.50 1040 12860 200 +4.3 -50.4 1.2 .times. 10.sup.1313 0.100 0.800 0.100 MnSb 1.00 1030 11430 63 +1.3 -43.7 1.2 .times. 10.sup.1214* 0.100 0.800 0.100 MnSb 3.00 1000 7420 212 -3.4 -39.8 5.0 .times. 10.sup.1115 0.100 0.800 0.100 MnNb 1.00 MnW 0.50 1000 10840 174 -5.3 -48.3 1.2 .times. 10.sup.1316# 0.200 0.700 0.100 -- -- 1000 21350 410 -6.3 -54.0 1.0 .times. 10.sup.1317* 0.200 0.700 0.100 MnNb 0.30 1000 20140 280 -5.1 -53.1 1.2 .times. 10.sup.1318 0.200 0.700 0.100 MnNb 0.50 1000 18430 172 -3.5 -50.6 1.0 .times. 10.sup.1319 0.200 0.700 0.100 MnNb 1.30 1000 16430 74 +0.8 -48.2 8.0 .times. 10.sup.1220 0.200 0.700 0.100 MnNb 2.50 1000 11130 168 +4.3 -39.2 6.0 .times. 10.sup.1221* 0.200 0.700 0.100 MnNb 5.00 980 6990 254 +5.3 -36.4 1.0 .times. 10.sup.1122* 0.200 0.700 0.100 MnW 0.10 1000 20410 313 -3.1 -50.1 1.0 .times. 10.sup.1323 0.200 0.700 0.100 MnW 1.00 990 16890 174 -3.1 -50.1 8.0 .times. 10.sup.1224 0.200 0.700 0.100 MnW 2.00 980 13380 184 +0.6 -43.2 5.0 .times. 10.sup.1225* 0.200 0.700 0.100 MnW 5.00 940 8190 205 +3.2 -39.3 2.0 .times. 10.sup.1126* 0.200 0.700 0.100 MnSb 0.10 1000 20030 305 -5.1 -53.1 1.5 .times. 10.sup.1327 0.200 0.700 0.100 MnSb 0.50 1000 18630 200 -3.5 -51.2 1.5 .times. 10.sup.1328 0.200 0.700 0.100 MnSb 1.00 1000 13340 106 +0.6 -43.9 1.0 .times. 10.sup.1329 0.200 0.700 0.100 MnSb 2.50 1000 10140 184 +4.3 -39.3 4.0 .times. 10.sup.1230* 0.200 0.700 0.100 MnSb 5.00 980 8430 213 +4.9 -39.4 1.0 .times. 10.sup.1131# 0.250 0.550 0.200 -- -- 980 12110 90 +4.4 -55.0 8.0 .times. 10.sup.1232* 0.250 0.550 0.200 MnNb 0.30 980 11980 85 +3.1 -51.3 9.0 .times. 10.sup.1233 0.250 0.550 0.200 MnNb 0.50 980 10830 35 +2.1 -49.3 8.0 .times. 10.sup.1234 0.250 0.550 0.200 MnNb 1.00 980 10400 65 +0.3 -45.3 7.0 .times. 10.sup.1235 0.250 0.550 0.200 MnNb 2.50 980 9125 168 +5.4 -39.8 5.0 .times. 10.sup.1236* 0.250 0.550 0.200 MnNb 5.00 960 6050 256 +6.9 -37.4 1.0 .times. 10.sup.1137* 0.250 0.550 0.200 MnW 0.30 980 11480 84 +3.3 -53.9 1.0 .times. 10.sup.1338 0.250 0.550 0.200 MnW 1.50 960 10350 45 +1.2 -49.8 7.5 .times. 10.sup.1239* 0.250 0.550 0.200 MnW 3.00 960 9420 212 -4.1 -36.3 4.5 .times. 10.sup.1240* 0.250 0.550 0.200 MnSb 0.30 980 11490 90 +4.3 -52.0 9.0 .times. 10.sup.1241 0.250 0.550 0.200 MnSb 1.00 980 10640 122 +4.1 -50.6 9.0 .times. 10.sup.1242 0.250 0.550 0.200 MnSb 2.00 980 7130 178 +2.1 -46.3 7.5 .times. 10.sup.1243* 0.250 0.550 0.200 MnSb 5.00 980 4130 105 +4.0 -50.1 5.0 .times. 10.sup.1144 0.250 0.550 0.200 MnNb 0.50 MnW 0.50 980 11430 105 +4.0 -50.1 7.0 .times. 10.sup.1245 0.250 0.550 0.200 MnNb 0.50 MnSb 1.00 980 11580 132 +1.4 -42.3 5.0 .times. 10.sup.12__________________________________________________________________________ Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub. 1/2 W.sub.1/2).sub.z O.sub.3 Note 2: Compositions of the Nos. with asterisk (*) are outside the scope of the present invention with sharp (#) are included in the claim 1. Note 3: Additive elements MnNb means Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Mn means Pb(Mn.sub.1/2 W.sub.1/2)O.sub.3 and MnSb means Pb(Mn.sub.1/3 Sb.sub.2/3)O.sub.3.

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20.degree. C. under application a D.C. voltage of 1000 V.

From TABLE 4 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Pb(Mn.sub.1/2 W.sub.1/2)O.sub.3 and Pb(Mn.sub.1/3 Sb.sub.2/3)O.sub.3 in an amount in total quantity equivalent 0.50 to 2.50 weight % exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant along with low sintering temperature.

The reasons for the limitations in TABLE 4 are as follows.

If contents of Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Pb(Mn.sub.1/2 W.sub.1/2) and Pb(Mn.sub.1/3 Sb.sub.2/3)O.sub.3 in total is smaller than 0.50 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 2.5 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

As apparent from these Examples 1 to 4, the ternary ceramic compositions of the present invention have low sintering temperature below 1100.degree. C., so that relatively cheap metal or alloy such as silver-30% palladium can be employed as internal electrodes of multilayer ceramic capacitors, and the durability of furnace used for sintering use may be extended and electric power for sintering may be lowered. Moreover, the ceramic compositions according to the present invention exhibit high dielectric constant together with high specific resistivity, low temperature coefficient of the dielectric constant and low dielectric loss. Therefor, the ceramic composition in accordance with the present invention are suitable for use in ceramic capacitors.

It will be evident that the starting materials to be used in the present invention are not limited to those used in the above-mentioned examples. Other oxide or compounds which are easily decomposed at elevated temperature may be used in place of the starting materials of the above examples.

Claims

1. A ceramic compositions comprising a substance represented by the formula

PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x,y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 ternary system.

2. A ceramic composition comprising a substance represented by the formula

PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x, y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 ternary system and at least one element selected from the group consisting of Mn, Cr, Co and Mo in an amount in total equivalent to from 0.03 to 0.60 weight percent of respective oxides MnO.sub.2, Cr.sub.2 O.sub.3, CoO and MoO.sub.3.

3. A ceramic composition comprising a substance represented by the formula

PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x, y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 ternary system and at least one element selected from the group consisting of Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Pb(Mn.sub.1/2 W.sub.1/2)O.sub.3 and Pb(Mn.sub.1/3 Sb.sub.2/3)O.sub.3 in an amount in total equivalent to from 0.50 to 2.50 weight percent.