DE2361230A1 - Barium-strontium titanate-bismuth oxide ceramic dielectric - contg. titanium dioxide, giving high dielectric constant and low loss - Google Patents

Abstract

Ceramic dielectric based on BaTiO3 and SrTiO3 with added Bi2O3 contains 18-70 (wt.) % SrTiO3, 4-75% BaTiO3 and 2.5-17.4% Bi2O3 and also contains 1.7-20% TiO2, the TiO2/Bi2O3 wt. ratio being between 1 and 18. The dielectric can also contain small amts. (pref. 0.2-0.5%) of clay and/or oxide(s) of Mn, Cr, Nb, Ta, Fe, Co and/or rare earths such as La and Ce; whilst less than 30% of the total amt. of SrTiO3 and BaTiO3 can be replaced by CaTiO3, ZnTiO3, MgTiO3 and/or CdTiO3 or less than 50% of these by PbTiO3; and less than 30% of the total amt. of TiO2, SrTiO3 and BaTiO3 by ZrO2, SnO2 and/or HfO2. The ceramic is used in vacuum or gas circuit breakers and arrestors, voltage multiplier rectifiers in television receivers or oscilloscopes etc.

Description

Patent attorneys Augsburg 31. P.O. Box 242

Rehlingenstrasse 8 Postal checking account: Munich No. 745 39

6566 / Ol / UO / gn

TDK ELECTRONICS CO., LTD.

I ¹ IG ₁ Uchikanda 2-chome, Chiyoda-ku

Tokyo / Japan Composition of a ceramic dielectric.

The present invention relates generally to the composition of a ceramic dielectric and, more specifically, the composition of a ceramic dielectric with high dielectric constant and low dielectric loss. In addition, the ceramic Dielectric according to the present invention the changes in the dielectric constant and the dielectric Loss when the applied voltage changes over a large area is relatively small.

Ceramic dielectrics with high dielectric constant and low dielectric loss and also without changes in dielectric constant and dielectric loss over a wide range of applied voltage instead of known ceramic di-

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Elektrika in certain devices or circuits with high AC voltages would be very useful. Examples of such devices or circuits are: vacuum or gas circuit breakers and Holders (locking devices) or ceramic bushings, in which a ceramic dielectric used to improve the uniformity of distribution of a high AC voltage; Transmission systems using ceramic dielectrics to absorb traveling wave voltage; Pulse voltage measuring devices in which ceramic dielectrics work as voltage dividers. Ceramic dielectrics with the above-mentioned properties are also used in ce devices or circuits with high DC voltages, such as voltage multipliers, are very useful Rectifiers for television receivers or oscilloscopes.

The state-of-the-art ceramic dielectrics for high AC and DC voltages, those in the devices or circuits mentioned above are mainly made of barium titanate and small amounts of other materials, such as titanates and stannates. The prior art ceramic dielectrics are behaving but not in the above-mentioned devices or circuits with high AC or DC voltages especially good, because with them the changes in the dielectric constant and the dielectric loss are relatively large over a wide range of applied voltage. An example of a ceramic Dielectric that is used in devices or switching

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high voltage circuits, as mentioned above, is used in U.S. Patent 3 352 697. The dielectric ceramic materials described there consist of a sintered mixture of 20 to 90 percent by weight pre-sintered SrTiO », 3 tois 60 weight!? - percent Bi 0 and 5 to 60 percent by weight of TiO. The ceramic dielectric used in this

US patent mentioned, however, has the disadvantage that it is very expensive to manufacture on an industrial scale is because it contains a large amount of Bi 0. Another disadvantage of the ceramic dielectric according to the US patent is that it does not have a sufficiently high dielectric constant.

The main object of the present invention is a composition of a ceramic dielectric, that has a high dielectric constant, low dielectric loss and almost no © Ver change in dielectric constant and dielectric loss over a wide range has turned high DC and AC voltages.

Another object of the present invention are substances which, in small amounts, form a base composition of the ceramic dielectric according to the present invention and result in the sintered ceramic dielectric being dense and uniform.

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By achieving the main object mentioned above, the present invention has not been achieved the disadvantages of the ceramic dielectric described in US Pat. No. 3,352,697. The ceramic dielectric according to the present invention has a high dielectric constant and is inexpensive to manufacture as the Bi 0 of the US patent is partially replaced by BaO.

The present invention will now be more fully understood from the following description and drawing explained. Show it:

1 shows the changes in the dielectric loss factor tan (P (in %) of ceramic dielectrics both according to the prior art and according to the present invention when the applied alternating voltage gradient changes (in V / mm);

2 shows the changes in the characteristic ratio / ^ c / c (in %) of ceramic dielectrics both according to the prior art and according to the present invention when the applied alternating voltage gradient is varied (in V / mm).

In order to achieve the main object mentioned, the present invention provides a composition of ceramic dielectric, which is a mixture

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from 7 to _f l ^ 9t9 weight percent Strontiuraoxyd (SrO); 0.7 to 2Ö, 8 percent by weight diismuth tri-

oxide (Bi 0); 32.3 to 67.4 weight percent Titan's j

dioxide (TiO) and 2.6 to 49.3 percent by weight Barium Oxide (BaO) includes. Compared to the prior art, such a mixture has both a high dielectric constant as well as low dielectric loss,

The present invention will now be described with reference to FIG. Examples with reference to Tables I, II and III described.

example 1

A predetermined amount of strontium carbonate (SrCO ₀ ) and a predetermined amount. Amount of titanium dioxide (TiO) are mixed and pre-sintered at 1150 ° C for two hours. The pre-sintered mixture is then ground into powder, whereby strontium titanate (SrTiO ₀ ) is obtained. SrTiO ₀ , TiO_, Bi ₀ O ₀ and BaO (can be exchanged for BaCO) are then mixed with the weight ratios (percent) as indicated in columns 1 and 2 of Table I. After adding binders, the mixture obtained is pressed and shaped into disks 16.5 mm in diameter and M) mm thick under a pressure of 2000 kg / cm. Then the molded bodies are sintered for two hours at between 1100 and 13ΟΟ C, whereby sintered ceramic bodies are obtained. Then the. opposite sides of the resulting ceramic body painted with silver electrode paste. After painting

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the ceramic body is made with silver electro-speech paste heated in air to about 800 ° C. In this way, the painted silver electrode material becomes plated on the surfaces of the ceramic body.

Column .1 of Table I shows, in percent by weight, various ratios of the materials SrTiO, BiO, TiO and BaTiO in eighteen samples which were produced by the same method mentioned above. Column 2 of Table I shows the compositions (in percent by weight) of the ceramic dielectrics of the respective samples expressed in oxides (these oxides are SrO, Bi 0, TiO and BaO). Columns 3, 3, 5 and 6 of Table I show the various electrical characteristics of the respective samples. The dielectric constant έ with an alternating voltage of 5 volts and one KHz, the dielectric loss factor tan cT in percent with an alternating voltage of 5 volts and one KHz, the change ratios of the characteristic data Λ c / c .. in % and Δ c / c in % at an effective alternating voltage of 0.5 kV / mm and the change ratios of the characteristic data Δ c / c in % with a direct voltage of 1.5 kV / mm of the corresponding samples are shown in columns 3, 4, 5 and 6, respectively. The change ratios of the characteristic data Δ c / c. and / \ c / c in Ta-

1 - 2

Belle I are defined as follows.

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f at 0.5 KV / mm, 50;

or, 5 KV / mm DC voltage /.

hey

/ at 0.5KV / mm, -5SHz, \ I or. \ I 1.5 KV / mm DC voltage I _2 voltage '/ _{χ 100}

tan

It should be noted in Table I that Samples 1 and 15 are outside the scope of the present invention and Samples 19, 20 and 21 are examples of the prior art. These samples were included in Table I for comparison.

Fig. 1 shows the change in the dielectric loss factor tan cP (in %) of the ceramic dielectric of the sample 8 according to the present invention ^ the changes in the dielectric loss factor tan <f (in %) of the samples 1 and I5, which are outside the present invention , and the changes in the dielectric loss factor tan tT (in %) of samples 19, 20 and 21, which correspond to the prior art. In Fig. 1, the changes in the di * - electrical loss factor ο are shown as a function of the applied effective alternating voltage per mm at 50 Hz. *

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FIG. 2 shows the change in the change ratio / X c / c of the characteristic data (in %) of all * of the ceramic dielectrics of FIG. 1 mentioned above in the same way as in FIG. 1. The change ratio Δ c / c of the characteristic data in Fig. 2 is defined as follows:

a . _v \ / at an applied alternating) Δ ₁ = CZC tv Mil j "L V P ^{s ann} ungsgradienten, 50Hz /

t / at 5V, \

C- Vj KHz /

As can be seen from Table I and FIGS. 1 and 2, the ceramic dielectrics according to the present invention have a high dielectric constant and low dielectric loss and also almost no changes in dielectric constant and dielectric loss when the applied alternating or dielectric loss varies DC voltage. That is, the dielectric constant ξ is between 1000 and ^ 700, the dielectric loss factor tan tf is between 0.1 and 1.3% and the change ratio of the characteristic data Δc / c., As explained above, is between 0.8 and 19% for AC voltage and between --17 and -1.2% for DC voltage. In a preferred embodiment of the present invention, the composition of a ceramic dielectric consists of: 10 to k0 percent by weight SrO; 2.5 to 18.5 percent by weight Bi 0_; 35 to kl weight percent TiO and 2.5 to 53 weight percent BaO.

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Example 2

In the present invention one obtains a · ceramic dielectric, when the materials, of the ceramic dielectric are sintered as shown in column 1 of Table I. It is well known that a dense and uniform ceramic dielectric is obtained by adding a small amount of a mineralizer to the materials of which the ceramic dielectric is composed and then sintering the materials and the Miera. It is also well known that the f mineralizer prevents the ceramic dielectric from being reduced by the air during the sintering process. However, the various electrical characteristics of the ceramic dielectric, as shown in columns 3, 4 and 5 and 6 of Table I, should not be sacrificed in making the ceramic dielectric dense and uniform. In this example 2 becomes the

/ from Sample 2 shown in Table I and 39 »3 percent by weight SrO, 17.4 percent by weight Bi ₃ O ₃ , 40.5 percent by weight TiO and 2.8 percent by weight

BaO is made, a little mineralizer added. Three types of fabrics are selected for the mineralizer. These are manganese carbonate (MnCO), clay and Dilanthaii trioxide (La 0). As from column 2 of table II can be seen, the six samples 22, 23, 24, 25, 26 and 27 are produced as examples, Samples 22 and 23 containing 0.2 and 0.5 percent by weight MnCO respectively, samples 24 and 25 0.2 and 0.5 percent by weight, respectively. 0.5 percent by weight of clay and the samples and 27 contain 0.2 and 0.5 percent by weight of La 0, respectively. Column 1 in Table II shows the composition of the ceramic dielectric of the corresponding

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Samples 22 to 27, expressed in oxides with the composition of Sample 2 as shown in column 2 of Table I matches. The columns 3, ^, 5 and 6 of Table II give the electrical Characteristics and are the same as the corresponding columns e in Table I. The sample is inserted in Table II to show the differences de between the electrical characteristics of the sample with mineralizer and sample 2 without mineralizer make clear.

As can be seen from Table II, the electrical Characteristics of Samples 22-27 with the mineralizer as good as Sample 2. However, if so added more than 0.5 percent by weight of mineralizer to the ceramic dielectric materials the electrical characteristics will be extremely poor and therefore should be less added as 0.5% by weight of the mineralizer will. After an experiment carried out in view of the present invention, fewer should than 0.3 weight percent mineralizers can be added to get proper electrical ratings to obtain; More than 0.1 percent by weight mineralizers can use the sintered ceramic Make dielectric tight and even. Accordingly, it should be between 0.1 and 0.3 percent by weight Mineralizers the materials shown in columns 1 and 2 of Table I in the Practice to be inflicted. It should be noted that the same advantage that the ceramic dielectric is made dense and uniform by the addition of a mineralizer, not just when in use of sample 2, but also when using the

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Samples 3 through 18 in Table I were achieved. It it should be recognized that the mineralizers are not limited to those shown in column 2 of Table II. The mineralizer Other compounds including, for example, MnO can be substituted for MnCO. In this Traps are of course the weight percentages of this Compounds including MnO to be added, different from those of MnC0 ", shown in column 2 of Table II. The weight percent of these compounds inclusive However, MnO, as mentioned above, should be below 0.5 percent by weight »The sintered ceramic Dielectric can also be made dense and uniform - "by adding to the materials that are in As shown in column 1 of Table I, at least one of the following mineralizers is added: Oxides of manganese, 'chromium, tantalum and niobium', compounds of elements of the iron group such as iron or cobalt and rare earth compounds such as lanthanum or cerium.

Example 3

The main object of the present invention can also be achieved by using the divalent metals, these are Ba and Sr, and the tetravalent metal, that is Ti, is replaced by other bivalent or tetravalent metals are replaced.

In the case of sample 8, which is shown in Table I and consisting of 20.6 percent by weight SrOj 9 ?! Weight percent Bi 0; 37, k percent by weight TiO and 32.9

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By weight percent BaO, the divalent metal oxide is BaO by another divalent one Metal oxide (PbO) and the tetravalent metal oxide TiO by another tetravalent metal oxide

(Zr0) replaced. The various electrical characteristics, as shown in columns 3, _5, 4, 5 and 6, however, should not be worsened by this exchange. As can be seen from Table III, the four samples 28, 29, 30 and 31 were prepared as examples. In samples 28 and 29, 10 and 20 percent by weight of the BaO of sample 8 were replaced by PbO. In Samples 30 and 31, 10 and 20 percent by weight, respectively, of the TiO of Sample 8 were replaced by ZrO. This exchange is shown in columns 1 and 2 of Table III. Column 1 of Table III shows the composition of the ceramic material of the corresponding samples (28 to 31) in terms of oxides. The compositions of SrO and Bi 0 "

2 i

are the same as in column 2 of Table I for sample 8. Columns 3, 4, 5 and 6 of Table III give the electrical characteristics and are the same as in the corresponding columns of Table I. Sample 8 "is in the Table III introduced to clarify the differences between the electrical characteristics of sample 8 and sample 8 affected by the exchange

Wxe from columns 3 to 6 of Table III is apparent, the electrical characteristics of the sample 8 do not deteriorate when a substance of the Sample 8 is partially replaced by other substances that are chemically the same as the original substances of the Match sample 8.

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Generally speaking, the divalent metals like Sr or Ba, de can be found in columns 1 and 2 of Table I are replaced by other divalent metals such as Ca, Zn, Mg, Cd or Pb will. Also, the tetravalent metal (such as Ti) shown in columns 1 and 2 of Table I can be used can be replaced by another tetravalent metal such as Sn, Hf, or Zr. If the bivalent Metal is replaced by another divalent metal, part of the Sr and / or a Part of the Ba can be replaced by Ca, Zn, Mg, Cd or Pb. In this case, it should be less than 30 percent by weight SrO or BaO are replaced by a compound that contains Ca, Zn, Mg, or Cd, and less than 50 percent by weight of the 'SrO or BaO should be replaced with Pb, while less than 30 weight percent TiO by a compound that contains Sn, Hf, or Zr should be replaced.

In the above-mentioned embodiments, SrO and BaO are used in the form of carbonates. However, other forms, for example the hydrochloride of SrO and BaO, can also be used.

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Table I.

Dec 6, 1973

Per .. With SrTiO 1 percent I. TiO ₂ i Starred BaTiO i SrO 2 TiO ₂ BaO *. * * be 18.2 Weight lying invention _c η α
SLUJy Weight rehearse Weight Weight Weight No. Proportion of substance. 17.4 percent percent ■ 8? S / percent Oxide content percent percent I. 9.1 9.1 - 41.0 ^Bi 2 ° 3 40.8 - under the ι ~~ - ~
Weight-wt. 15.4 8.7 4.3 39.3 Weight 40.5 '2.8 - percent 12.7 20 * 1 4.4 37.5 percent 50.5 2.9 ff ι 72 * 7 16.7 7.7 15.4 34.7 18.2 39.8 10.1 2 69.6 10.9 6.4 30th 28.7. 17.4 38.9 19.7 3 66.4 9.1 2.4 30th 28.7 ' 9.1 34.9 19.7 4th 61.5 5 '. 7th 5.5 40 24.6 15.4 38.2 . 26.3 5 5Q.9 7.3 4.5 50 20.6 12..7- 37.4 32.9 6th 50.9 4.8 9.9 50 20.6 16.7 42.8 32.9 7th 43.6 4.5 3.6 60 16.4 10.9 36.9 39.4 8th 36.4 5.1 2.4 73.4 11.0 9.1 36.0 48.2 9 36.4 4.0 2.3 75 10.3 3.7 35.9 49.3 10 29.1 3.7 1.7 75 10.3 7.3 35.3 49.3 11 19.4 2.5 2.8 75 10.3 4.8 36.4 49.3 12th 18.2 5.0 1.8 80 8.2 4.5 35.5 52.6 13th 18.2 10 2.5 50 25.4 5.1 39.2 32.9 14th 18.2 - 15.0 50 16.9 4.0 45.2 32.9 * 15 14.5 10 50 16.9 3.7 40.2 32.9 16 45 - - BaTiO ₃ 2.5 CaTiO ₃ MgTiO ₃ . 17th 30th 64.5 5.0 10.9 5.7 18th 30th - - BaTiO ₃ 10 Bi ₂ (SnO ₃ ) 3 - 19th -. " 88.0 BaZrO ₃ 12.0 - BaTiO ₃ 18.9 20th - 94.1 Bi ₂ (SnO ₃ ) ,, fall 5.9 21 to * 0460 not

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Table I (continued)

sample 3 at 5V Wfech
self-tensioning
u. 1 KHz - 5 6th No. £
at 5V change
self tension
and 1 KHz 0.1, at 0.5V / mm We-
Alternating voltage
and 50 Hz at 1.5 KV /
ram same
tension * 1 960 Oil + ii 0.4 :: ■ 2 ".llOiO 0.12 +1.0 0.1 ■ - ■■ -: \ 3 1070 0.1 +2.1, 0.3; ■ ' .-- 2V2-:. ■ 4th 1240 0.1 +1.3 0.15 -2.7 ' 5- 1260 0.4 +0 _t 8 0.1 -1.8 .6. 1200 0.1 +1.8. ^; 0.8 +2.8 7 .. '". 1430 0.1 +2.0 -, 0.2 "-3.0 8th 1780 . 0.1 +1.8 · .0.1 • ^ 3.0 9. 1680 0.1: +2.3 ... 0.2 -3.7 10 2580 1.2. +2.5: r 0.15 -6.7 3810 .1.3. · +16.0; 1.8 -14.2 ir 4140 1.3: +17.5 2.0 -13.8 13th 4650> .1.1 +16.8 · 2.0 -I6.7 14th 4230 v.v .3.8;, '■■ " +18.7 2.3 -17.1 * 15 2350. +35.0: 6.8 -29.0 ■ 16 ... 1470. +0.8:; .0.1 '' -1.2 17 ..; -: 2170 + 2.8 ^■: -l "3 -5.7 18 - 1950. ■ '■' 0.7 ' +6.7. _; Λ | Χ _: Β ^ · -10.8 19th 2700 1.2 +22.8 4.1 -33.5 20th 1600 .'2.0
-: '.. -.;. +45.0 ij & 'Q' -13.8 21 2600 ", +114.0 26.7 -25.7

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Table II

Dec 6, 1973

sample SrO L. TiO ₂ BaO Mineralizer share ■ MnCO ₃ - Clay La ₂ O ₃ - No. .Weight. Oxide content Weight Weight Weight 0.2 Weight Gew> % - Bi ₂ O ₃ % % % 0.5 ^% % J - 39.5 Weight 40.5 3.0 - - do % do do - - 2 do 17.0 do do - - 0.2 " 22nd do do do do 0.2 0.5 23 do do do do 0.5 24 do do do do - 25th do do do do - 26th do 27 do

Table II (continued)

sample 2 3, . 4th 5 4c / ö ₂ 6th No. 22nd at 5V alternating
self tension
and 1 KIIz tan, / ü
at 5V
Alternating chip
tion and
1 KIIz at 0.5 KV / mm
Alternating chip
voltage and 50 Hz at 1.5KV /
mm Equal
tension
c / c 23 l \ c / c 0.Ü . ( ^C / o). - '24 1110 O _f 0l • (%), ■ 0.12 -1.7 25 ' 1142 0.1 +0.1 0.12 -2.2 - 26th 1109 0.2 +1.2 0.1 -2.3 • 27 1090 ' 0.1 +1.4 0.1 -2.5 922 0.1 +1.2 0.1 -2.7 1050 0.1 +1.2 0.6 -2.1 988 0.07 +1.0 -2.1 +1.0

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1 A% Table III SrO
Weight Bi ₂ O,
Weight
%. TiO ₂
Weight 2361230 BaO
Weight PbO
Weight ZrO ₂
'"Weight"
ο /
/ ο sample
No. 20.6
do
do
do
do 9.1
do
do
do
do 37 * 4
37.4
37.4
33.66
29.92 2 · ' 32 »9
29.61
26.32
32.9
32.9 3.29
6.58 <3.74
7-.4Θ 8th
28
29
30th
31
* Oxide content Oxide content '

Table III (continued)

sample
No. 3 4th VJl AoZc ₂ W) 6th 8th 6th
at 5V
Change
tension
and 1 KHz tan,%
at 5V
Change
tension
and 1 KHz 0.1 at 1.5 KV /
mm Equal
tension
-Ac / c, ~ 28 1780 0.1 at 0.5 KV / mm change
self tension and
50 Hz - 0.1 -3.0 29 1750 0.15 4 0 / C ₁ m 0.2 -3.1 30th 1740 0.15 +1.8 0.3 -2.5 31. 1680 0.15 +1.4 0.3 -2.7. . 1650 0.15 * 2.0 -2.4 +1.7 +1.5

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Claims (6)

cLu Ha A- ην. & .ι2.1τ Rudolf Busselmeier Dipl.-Ing. * KolfCharrier rewriting: Patentanwälte _, e9ooA ««. Br «3i" .P ... f.cha «A2 ·· P 23 61 230.8-34 8 ·. Note: TDK Electronics Co. Ltd. Poslsdieckkonto: Munich No. 74S3J 6566/01 / Ch / Fr Augsburg, December 27, 1974 claims 1. Ceramic dielectric with a predominant proportion of barium and strontium titahates and an addition of bismuth oxide, characterized in that the weight proportion of SrTiO- * is about 18 to 70 %, that of BaTiO ^ about 4 to 75 % and that of BipCX 2 5 to 17.4% by weight and the dielectric has to about 20 wt.% TIOP 1.7, wherein the TiO GewichtsverMltnis between ₉ and Bi O ^ ₀ is between about 1 and 18. 2. Ceramic dielectric according to claim 1, characterized in that it is in a small amount Contains at least one of the substances: clay, manganese oxide, chromium oxide, niobium oxide, tantalum oxide, iron oxide, cobalt oxide and oxides of rare earths such as lanthanum or cerium .. 3. Ceramic dielectric according to claim 1, characterized in that less than 30 wt. % Of the total amount of strontium and barium titanates replaced .. is replaced by at least one of the titanates CaTiO ,, ZnTiO ^, MgTiO ^ and CdTiO ^. 509825/0460 6566/01 / Ch / Fr December 27, 1974 4. Ceramic dielectric according to claim 1, characterized in that less than 50 wt. % Of the total amount of strontium and barium titanates is replaced by PbTiO ^ ,. 5. Ceramic dielectric according to claim 1, characterized in that less than 30 wt. % Of the total amount of TiO ₂ , SrTiO, and BaTiO ₃ is replaced by at least one of the oxides ZrOp, SnO ₂ and 6. Ceramic dielectric according to claim 2, characterized in that the small amount is between 0.2 and 0.5 wt. % . 509825/0460