DE2411639B1 - Ceramic dielectric - Google Patents

Description

3 4

and those ceramic dielectrics that cannot get into the even sintered ceramic body,

Fall within the scope of the present invention; adding a very small amount of clay, such as

F i g. 2 shows the dielectric loss factor tan <5 silicon or aluminum oxide of the mixture, plus

(in%) by ceramic dielectrics according to the state or by adding manganese dioxide (MnO ₂ )

the technique and according to the present invention 5 by another metal oxide from other metals,

is offset as a function of the applied alternating voltage, such as Fe or Co,
served (in kVen / mm); The method of obtaining a sintered

F i g. 3 the change ratio A C ₅ (in%) ceramic body, which was mentioned above, the electrostatic capacity as a function of the an- is of course not the only possible one. DC voltage gradients in kV / mm given by way of example, the sintered ceramic body can also have ceramic dielectrics that are within the range of the above-described ceramic dielectrics which fall as the present invention. Predetermined amounts of electrics that do not fall within the scope of the present SrCO ₃ , TiO ₂ , Bi ₂ O ₃ , MgCO ₃ and at least one oxide invention, and the ceramic dielectric of a rare earth are mixed and presintered, according to the state of the art, 15 Then the pre-sintered mixture is pulverized

F i g. 4 the dielectric constant (e _s ) and the grind. The powder of the presintered mixture is made

Dielectric loss factor (tan δ in%) as a function after adding some binders and pressed

the prevailing temperature for the ceramic di- shaped into disks; then the molded

Elektrikum according to the present invention and sintered body. In this way one obtains

the ceramic dielectric according to the state of the 20 sintered ceramic bodies. The electrical properties

Technology. shafts of the sintered ceramic body, which through

Now the present invention will be obtained by means of this method, of course agree

Examples described with reference to Table I. match those of the sintered ceramic bodies, obtained by the above-mentioned method

Example ^Z 5 are.

Column 1 of Table I shows various relationships

A certain number of mole percent strontium of the basic materials SrTiO ₂ (in mole percent), carbonate (SrCO ₃ ) and the same number of mole percent Bi ₃ O ₃ (in mole percent), TiO ₂ (in mole percent) and MgO titanium dioxide (TiO ₂ ) are mixed and 2 hours pre-sintered (in weight percent) for 33 sample Nos. 1 to 34 with long at 1150 ⁰ C. Then the previous exception of No. 33, which was ground into powder according to the same, top-sintered mixture, whereby the processes mentioned were produced. The sample receives SrTiO ₃ . SrTiO ₃ , TiO ₂ , Bi ₂ O ₃ , MgO - which is added as No. 33 in Table I, which has an asterisk, is an MgCO ₃ , and at least one of the is - examples of the prior art, and the samples Tenen earths are then circled in the molar or weight nos. 1, 3, 7, 8, 11, 24, 27, 30, 32, 34, their number ratios (%), as in columns 1 and 2 of 35 is outside the range given in Table I, mixed; invention related to this mixture. Column 2 of Table I continues to give 0.1 percent by weight of MnO ₂ as what for and in what amounts (in weight mineralizers added. The resulting mixture percent) rare earths in the form of oxides in the after adding some binders Corresponding specimens contain or not contain presses and are in disks of 16.5 mm 0 and 1 mm thickness 40. Columns 3, 4, 5, 6 and 7 of Table I show shaped. The shaped disks are then sintered for 2 hours at 1100 to 130O ⁰ C for the various electrical properties; on these speaking samples. The dielectric constant s _s way one obtains sintered ceramic bodies. Then at an alternating voltage of 1 kHz and 5 V _e «, the two areas of the resulting ceramic dielectric loss factor tan δ in percent (at 1 kHz see body painted with silver electrode paste. 45 and 1 MHz), the change ratio Δ C ₁ the after painting with the silver electrode paste electrostatic capacity in% and the dielectric, the ceramic body is ^{heated in air to approximately a loss factor tan <5 in%, the latter two at 80O 0} C; In this way, the painted on an alternating voltage gradient of 0.5 kV / mm silver electrode material is plated on the sides of the ceramic and 50 Hz, the change ratio Δ C _{2 of} the body seen. Then, if necessary, 50 electrostatic capacity in% with an equal to the plated silver electrode, line connections, voltage gradients of 2 kV / mm and that are attached, and an insulation paste is painted on certain parts of the surface of the change ratio Δ C _{3 of} the electrostatic capacitance-ceramic body. capacity in% at -30 and +85 ⁰ C of the corresponding the different electrical properties of the samples corresponds are shown in columns 3, 4, 5, 6 and 7, respectively, speaking samples are measured as from the 55 The variation ratios Δ C ₁ , Δ C ₂ and Δ C ₃ columns 3 to 7 of Table I can be seen. the electrostatic capacity in Table I.

Through experiments required for the present er- defined as follows, where [C] is each the value

Findings were carried out, it was found that the electrostatic capacity at 20 ⁰ C means:

_{Δ c =} [C] at 5 Veii (1 kHz) - [C] at 0.5 kV _eff / mm (50 Hz) _
^1- [C] at 5Vea / mm (lkHz)

_At [C] at 5 Vefl (1 kHz) - [C] at 2 kV / mm (same voltage)

[C] at 5 Vefl (IkHz)

: - [C] at 85 ° ([C] at +20 ⁰ C

. _ [C] at +20 ⁰ C - [C] at 85 ° C or -30 ° _inn
Δ C ₁ = - ■ · IUU.

5 6

As shown in Table I. As can be seen, the samples have a large temperature change ratio which is within the range of the present invention electrostatic capacitance, for example -3000, has a high dielectric constant (s _s ) between ppm. This disadvantage of SrTiO ₃ was about 300 and about 1300, a small di- according to the invention by the addition of MgO electrical loss factor (tan <5) and a small 5 eliminated.

Variation of the change ratio Δ C _{3 of} the breakdown voltage of the ceramic dielectric

electrostatic capacity (in%) with the prevailing tricums according to the present invention is more the temperature. It follows from Table I that the electrostatic tricum according to the prior art is twice as high as in the case of the ceramic Dielek change ratios ΔC _3. For example capacity the variations between + 15 and -15% ίο is the breakdown voltage of sample no. 15 (± 15%). 12 kV / mm, while the breakdown voltage of the

Ceramic dielectrics, which in certain Preliminary Sample No. 33 is 4.5 kV / mm; The breakdown directions or circuit arrangements with high voltages are used here as voltage gradients from alternating or direct voltages. It is believed that the higher breakdown must, as already mentioned above, a low voltage of the ceramic dielectric according to the dielectric dissipation factor (tan δ), small variation of the present invention from the following circumstance ratio (Δ C ₁ and Δ C ₂ ) of the electrostatic originates from. The grains, which form the ceramic dielectric capacitance and small changes in the dielectric constant, crystallize out finely with diameters constant (s _s ) when the applied high changes between 1 and 2 μ, if MgO or an oxide have an alternating or direct voltage . The ceramic 20 rare earth is added. The addition of a see dielectric according to the present invention also improves the rare earth oxide so that these requirements can easily be met. This tano of the ceramic dielectric; As can be seen from the fact that the composition of the ceramic I can be seen, this effect is particularly noticeable in the dielectric according to the present invention if the frequency of the applied alternation is not relatively high for a ferroelectric substance such as barium voltage. The usefulness and the titanate (BaTiO ₃ ) contains, but rather SrTiO ₃ ent- advantages of the ceramic dielectric according to the holds. Accordingly, a para-electrical state of the present invention, compared with the state of the SrTiO ₃ in the ceramic dielectric, leads to the technique or compared to ceramic dielectrics, small changes in the dielectric loss trica which do not fall within the range of the present factor (tan S) of the change ratio (Δ C ₁ 30 finding, will be even clearer in the following with reference to and Δ C ₂ ) of the electrostatic capacity and the drawing.

Dielectric constant (ε), the last two at F i g. 1 shows the change ratio Δ C ₄ of FIG

Variation of the applied high AC or DC electrostatic capacity as a function of the thermal voltage. However, as is well known, SrTiO ₃ has the temperature in%, where Δ C ₄ defines the following disadvantage that it is 35 when the prevailing value is changed:

. _ [C] at +20 ⁰ C - [C] between -50 and + 150 ⁰ C "" _n

Δ Ca = · IOP.

[C] at + 2O ⁰ C

Here, [C] denotes a value of the electrical dissipation factor tan <5 at some specific points

static capacity. of the applied alternating voltage gradient up to

As shown in FIG. 1, Sample No. 15 measured 2.5 kVeft / mm (at 50 Hz). As shown in FIG. 2

which falls within the scope of the present invention, 50 can be seen, Sample No. 15 has one

with variation of the prevailing temperature an extremely low value, which is close to 0%

extraordinarily small variation of the change and an extraordinarily small variation of the di-

ratio of the electrostatic capacity. On the other hand, the electrical dissipation factor is tan <5. On the other hand, who owns

Samples Nos. 11 and 8 that do not have a large variation in tan δ between Sample No. 33

The range of the present invention falls, large 55 approximately 0 and 10%.

Variations of this ratio. F i g. 3 shows the variation of the change in change

F i g. 2 shows the variations in the dielectric ratio Δ C _{8 of} the electrostatic capacity in%

Loss factor tan δ in% for the ceramic Di- for sample no. 15, which is in the range of the present

Elektrikum of sample No. 15, which falls within the scope of the invention, sample No. 11, which does not fall within the range

present invention falls, and for the ceramic 60 of the present invention falls, and sample No. 33,

Dielectric of sample No. 33, which is the prior art; Δ Q is the following-

Technology. In Fig. 2 the dielectric dimensions were defined:

. _ [C] at 5Vefl (IkHz) - [C] between 0 and 2kVH / mm (same voltage) _inn

Δ C ₅ . = - · IUU.

[C] at 5Veii (lkHz)

7 8

Herein, [C] denotes the value of the electrostatic; a dense and uniform ceramic is obtained

see capacitance at 2O ⁰ C. by putting a certain amount of dielectric

As shown in FIG. 3 can be seen, has at least one of the following substances for the basic sample No. 15 an extremely small variation composition of the ceramic dielectric than of the change ratio of the electrostatic 5 mineralizers adds: clay or an oxide of Mn, Capacity with variation of the applied equal- Cr, Fe or Co. It is known that the mineralizer Stress gradients. For example, it is prevented that the ceramic dielectric through air change ratio of the electrostatic capacity during sintering is reduced and moreover of sample # 15 at 2.5 kV / mm in FIG. 3 the ceramic dielectric is still tight and even extraordinarily small, close to 0%, compared to the io power. However, it should be the various electrical Change ratios of Sample Nos. 11 and 33. Properties of the ceramic dielectric such as

F i g. 4 shows the variation in dielectricity - see columns 3 to 7 of Table I for example

constant s _s and the dielectric dissipation factor are shown, should not be sacrificed if the ceramic

Tan δ in% for sample No. 15, which made the dielectric dense and uniform in the mixing area

present invention falls, and sample No. 33 which is to be 15. Accordingly, the amount of

corresponds to the state of the art. As shown in FIG. 4 mineralizers are carefully chosen so that they

As can be seen, Sample No. 15 is extremely small within the limits where the various

Variations in dielectric constant and dielectric properties do not deteriorate,

electrical dissipation factor, compared with the sample The mineralizer Mn can for example as

can be added according to the state of the art when changing the 20 MnCO ₃ . Similarly, the

prevailing temperature. Mineralizer Cr for example added as Cr ₂ O ₃

The scope of the present invention can be made through. Of course, these mineralizers can too the details mentioned below, which are added to experiments than other compounds, which also ments and, more precisely, lead to the same effect in Table I, that the ceramic data are staked out. 25 Elektrikum is made dense and uniform; then

If less than 30 mol percent or more than 90 mol- sin Λ, however, the amounts of these compounds, the m-

percent strontium titanate must be joined in the ceramic dielectric, unlike MnCO ₃ or

are included, the dielectric constant e _s becomes Cr ₂ O ₃ . In this case, the amount of mineral

less than 290; as a result, for the practical sierers less than 0.5 percent by weight, based on the

Use of unsuitable dielectric creates. 30 Total weight of the basic composition of the ceramic

If more than 22 mol percent Bi ₂ O ₃ are still contained in the mixed dielectric according to the present ceramic dielectric, that will be the case. If more than 0.5 percent by weight of ceramic dielectric is a highly porous body and, on the other hand, the mineralizer in the ceramic dielectric is kept less than one percent by weight, various electrical Bi ₂ O _{3 is contained} in the ceramic dielectric, and the properties of the ceramic dielectric decrease various electrical properties, such as two-strong. The amount of mineralizer should therefore, for example, the change ratio of the electrical see 0.1 and 0.5 percent by weight, in which static capacity as a function of the prevailing limits, a dense, uniform ceramic Di-temperature is worse; thereby an electric material is obtained without deterioration of the various ceramic properties unsuitable for practical use can be obtained,
mixed dielectric. When more than 69 mol percent As explained above, the basic composition includes TiO ₂ in the ceramic dielectric, according to the composition of the ceramic dielectric, the dielectric constant e _s extremely of the present invention becomes 30 to 94 mol percent SrTiO ₃ , small; On the other hand, if less than 5 mole percent TiO ₂ 1 to 22 mole percent Bi ₂ O ₃ , 5 to 69 mole percent TiO _{2 is contained} in the ceramic dielectric, 45 and also 0.1 to 20 weight percent MgO, no dense, uniform ceramic dielectric moved onto the Total weight of the three compounds produced; one obtains a for the practical SrTiO ₃ , Bi ₂ O ₃ and TiO ₂ . In addition, 10 Ge can use unsuitable ceramic dielectric. If more than 20 percent by weight of MgO is contained in the ceramic earth, based on the total weight of the dielectric above, the basic composition mentioned is low in the ceramic electrical constant s _s , and additionally contains dielectric be. In such Zuwird it difficult to correct the ceramic dielectric composition is obtained sinter a ceramic Dielekzu, since a temperature over 1400 ⁰ C for trikum with excellent electrical properties; Sintering is required. On the other hand, if less than it has the high dielectric properties-0.1 weight percent MgO is contained in the ceramic body 55 constant, low dielectric loss and, there are deteriorations in the small variations in the change ratio of the effects leading to a high value of e _s and for the electrostatic capacity and the dielectric improvement of the change ratio of the electrical loss, the last two for the change in the static capacity with a change in the applied voltage. In addition, a mineralide temperature can result. If there are more than 10 percent by weight in the ceramic dielectric, percent of a rare earth oxide in the ceramic, thereby containing a dense, uniform ceramic dielectric, the dielectric can be produced,
electric constant e _{s of} the ceramic dielectric in the above-mentioned embodiments have become low. If, on the other hand, less than 0.01 weight, some raw materials in the form of carbonates, such as percent of a rare earth oxide in the form of SrCO ₃ or MgCO ₃ , are used. Mixing dielectric is included, but of course other forms are also obtained, for example advantages that are otherwise no longer achieved by adding an oxide of an oxide to the raw materials without reducing the rare earth. Also mentioned features are used.

ίο

Table I.

in 1 nt 12.0 24.1 i
weight 2 3 ι at 5 tan <5 6th J O) sample SrTiO ₃ Mole percentage TiO ₂ MgO 1
percent
oxide ε ,: at
5V _elt IMHz (%) at 2k \
AC _Z / ■ / mrn (same sp.)
ZlC ₃ +85 ⁰ C Bi ₂ O ₃ less common (IkHz) tan δ (»/")
at 5 V _eff 0.04 at 0.5 kVeff / mm
(50Hz) 0.04 -21.0 No. 77.7 20.9 0 Earth at 0.07 ZlC ₁ 0.04 ( ⁰ Io) -30 ⁰ C -15.5 (T) 77.3 1.8 20.9 4.8 0 517 IkHz 0.18 ( ⁰ Io) 0.55 0 +21.5 -16.7 2 74.7 1.8 16.7 0 0 457 0.02 0.33 +0.5 0.15 0 +13.5 -11.8 © 74.7 8.6 16.7 3.0 0 966 0.02 0.5 +0.6 0.05 -2.7 +18.7 -10.5 4th 74.7 8.6 16.7 5.3 0 1070 0.3 0.47 +1.8 0.08 -1.3 +7.0 -8.8 5 74.7 8.6 16.7 12.0 0 882 0.05 0.4 +1.0 0.08 -0.8 +4.8 -8.5 6th 74.7 8.6 16.7 20.5 0 742 0.03 0.4 +0.7 0.42 -0.5 +5.2 -19.0 © 72.3 8.6 20.6 0 0 475 0.03 0.7 +0.6 0.15 0 +4.7 -9.3 (?) 72.3 7.1 20.6 4.8 0 1050 0.03 0.4 +0.2 0.08 -2.6 +18.0 -8.7 9 72.3 7.1 20.6 4.8 0 961 0.3 +1.7 -0.8 +4.8 10 7.1 CeO ₂ 958 0.05 1.8 +1.0 1.8 -0.5 +5.1 -15.1 63.9 24.1 0 0.15 0.03 2.0 +1.0 0.15 -12.3 (B) 63.9 12.0 24.1 1.0 0 1080 3.4 0.1 -3.4 +14.3 -8.5 12th 63.9 12.0 24.1 2.4 0 1310 0.8 3.2 +2.5 0.05 -1.6 +9.8 -8.0 13th 63.9 12.0 24.1 2.4 0 1215 ο, ι 2.5 +1.1 0.04 -1.5 +4.8 -8.5 14th 63.9 12.0 24.1 2.4 La ₂ O ₃
0 1 1180 0.05 2.1 +1.0 0.04 -1.4 +5.0 -7.9 15th 63.9 12.0 24.1 2.4 U, J.
0.5 1150 0.03 1.1 +0.8 0.01 -0.8 +4.5 -8.0 16 63.9 12.0 24.1 2.4 1.0 1020 0.02 0.6 +0.5 0.01 -0.5 +4.8 -8.3 17th 63.9 12.0 24.1 2.4 3.0 970 0.02 0.06 +0.5 0.01 -0.5 +7.0 -7.8 18th 63.9 12.0 24.1 2.4 5.0 750 0.01 2.6 +0.1 0.04 -0.3 +7.1 -8.0 19th 63.9 12.0 24.1 2.4 10.0 480 0.01 1.9 0 0.03 0 +6.8 -8.5 20th 63.9 12.0 24.1 2.4 0.5 1082 0.01 0.7 0 0.01 -1.7 +4.0 -8.1 21 63.9 12.0 24.1 2.4 1.0 1010 0.02 1.4 +0.8 0.1 -1.3 +5.7 -9.7 22nd 52.1 12.0 38.4 4.8 5.0 722 0.01 1.4 +0.5 2.8 -0.5 +6.9 +1.3 23 36.0 9.5 42.5 0 0 957 0.01 0.55 +0.2 0.5 -0.8 +3.8 +5.8 ® 36.0 21.5 42.5 2.0 0 320 0.05 0.8 +0.7 0.3 -1.2 -1.8 +14.5 25th 36.0 21.5 42.5 10.0 0 410 1.1 2.0 +2.2 0.7 -0.2 -3.8 +66.0 26th 36.0 21.5 42.5 32.0 0 290 0.3 0.3 +0.2 0.15 0 -12.8 +12.0 © 36.0 21.5 42.5 2.0 0 193 0.2 0.25 +0.1 0.15 0 -42.0 -4.8 28 33.1 21.5 57.1 2.5 La ₂ O ₃
1.0
0 405 0.4 1.3 0 0.4 -0.2 -10.8 +70.4 29 31.2 9.8 45.9 20.5 0 387 0.1 0.3 +0.1 0.1 -0.1 +1.8 -18.0 29.5 22.9 67.9 3.0 0 215 0.07 0.11 +0.5 0.1 O' -48.0 -11.6 31 10.8 2.6 87.1 2.5 0 512 0.3 4.5 +0.5 10.0 -0.2 +19.0 -7.2 ® BaTiO ₃
98.0 2.1 Bi ₂ (SnO ₃
2.0 262 0.02 0.04 +0.3 0.01 0 +14.5 -7.3 * 33 63.9 2.4 CeO ₂ 1470 0.02 0 -18.5 +8.0 (5S) 15.0 278 1.2 +42.0 0 +5.0 0.01 0

For this purpose 2 sheets of drawings

Claims (4)

1 2 have a constant. In addition, the claims are: changes in the dielectric constant, the dielectric loss and the electrostatic capacitance 1. Ceramic dielectric with a content in the case of a change in the range of the applied voltage across SrTiO ₃ , Bi ₂ O _{3 and} TiO ₂ , markedly too large as a result; Finally, the change in the drawing that there is 30 to 94 mol percent SrTiO ₃ , electrostatic capacity when changing the 1 to 22 mol percent Bi ₂ O ₃ and 5 to 69 mol percent temperature is also too great,
percent TiO ₂ , also 0.1 to 20 percent by weight An example of a known ceramic dip percent MgO, based on the total weight of the elektrikum, is in the USA patent 3 352 697 three compounds SrTiO ₃ , Bi ₂ O ₃ and TiO ₂ , ent- io described. It is made up of 20 to 90 percent by weight holds. from SrTiO ₃ , 3 to 60 percent by weight Bi ₂ O ₃ and 5 2. Ceramic dielectric according to claim 1, up to 60 percent by weight of TiO ₂ . Good ones are characterized by the fact that fewer values are also achieved for the dielectric constant (than 10 percent by weight of at least one given value between 195 and 1100). Also contains the oxide of the rare earths. 15 Q values are satisfactory (values given 3. Ceramic dielectric according to claim 1, between 80 and 5000). On the other hand, the characters are thereby characterized in that there are at least one size limit for practical use contains the following substances: clay or an oxide, depending on the temperature. of Mn, Cr, Fe or Co. The object of the present invention is to provide a 4. Ceramic dielectric according to claim 2, 20 to create ceramic dielectric that has a high characterized in that it also has a minimum dielectric constant, an extraordinarily diluted Contains any of the following: clay, wrestling, dielectric loss, minor change or an oxide of Mn, Cr, Fe or Co. of the electrostatic capacity with the prevailing Temperature and minor changes in the dielectric 25 fresh loss and electrostatic capacity with the applied voltage. It is known in principle from German Auslegeschrift 1124 109, through the addition of oxides, z. B. of magnesium, based on dielectrics The invention relates to a ceramic dielectric 30 of strontium titanates the dielectric properties with a content of SrTiO ₃ , Bi ₂ O ₃ and TiO ₂ . damage, especially the loss factor. Ceramic dielectrics are said to have high dielectric flows. constant, low dielectric loss, good The object is achieved according to the invention by changing the ratio of the dielectric constant that the ceramic dielectric 30 to 94 mol as a function of the prevailing temperature and very 35 percent strontium titanate (SrTiO ₃ ), 1 to 22 mol small changes in the dielectric loss and percent of bismuth trioxide (Bi ₂ O ₃ ), 5 to 69 mol of the electrostatic capacity over a wide percentage of titanium dioxide (TiO ₂ ), as well as 0.1 to 20 Ge range of applied voltages. weight percent magnesium oxide (MgO), based on It would be very useful if such ceramic di- the total weight of the three components (SrTiO ₂ , Elektrika instead of the previously known ceramic 40 Bi ₂ O ₃ , TiO ₂ ) contains. Preferably that contains Dielectrics for certain devices or ceramic dielectrics according to the present invention processing arrangements with high AC voltages for the invention below 10 weight percent of at least Would be available. Examples of such devices - one of the rare earths. Circuits or circuit arrangements are: Vacuum- It is advantageous if the above-mentioned dielectric or gas circuit breaker, holding device or 45 also contains at least one of the following substances as ceramic feedthroughs, in which mineralizers are used: the metal oxides of manganese, improve the uniformity of the distribution high chromium, iron or cobalt; or sound. The above alternating voltages ceramic dielectrics used mentioned substances Bi ₂ O ₃ , TiO ₂ and MgO can be used well; Transmission systems in which _{combine with SrTiO 2} for absorption, in that one of these mineralisorption of voltage surges (traveling waves) is added to the ceramic. Then the ceramic dimic dielectric can be used; Meßvorrich- elektrikum according to the present invention equipments for pulse voltages in which ceramics are richly sintered; it results in a dense dielectric acting as a voltage divider. Ceramic uniform sintered ceramic dielectric. Dielectrics with the above-mentioned properties The addition of the metal oxide MgO and the rare would also in devices and circuits with 55 earth to the ceramic dielectric leads to higher DC voltages, as for example in the improvement of the change ratio of the voltage-multiplying rectifiers of remote static capacitance with the prevailing temperature or oscilloscopes, very useful. and minimizes the dielectric loss of the ceramic Well-known ceramic dielectrics for high uniformity of dielectrics; in addition, the to- and alternating voltages resulting in the aforementioned 60 additional advantage that the sintered ceramic di-devices or circuit arrangements used elektrikum, as mentioned, become tight and uniform, consist mainly of barium titanate and will make. a small amount of other substances, such as The invention will now be based on the drawing Titanates. The known ceramic dielectrics described in more detail: It shows however, show in the mentioned devices or 65 F i g. 1 the change ratio A C ₄ (in%) Circuits with high DC or AC voltage as a function of the electrostatic capacity inadequate behavior, since they are a prevailing temperature for ceramic dielectrics, high dielectric loss and low dielectric- which fall within the scope of the present invention,