DE2053889A1 - Ceramic dielectric - prepd from titanates and/or stannates of barium and bismuth - Google Patents

Abstract

Ceramic dielectric with dielectric coefft. of 700-2000 (1000), for electrical condensers, is prepd. by (I) mixing the oxides of Ba, Sn, Ti and Bi corresp. to a final compsn. of 55-85 wt. % BaTiO3, 5-20 wt% BaSnO3 and 0.5-5 wt % Bi2O3 and/or addn. of a mixt. of Bi2O3 and TiO2 and/or SnO2 and/or ZrO2 with single additive proportions of 1.2-20 wt % Bi2O3, 0.6-10 wt %. TiO2, 0.9-15 wt % SnO2 and 0.8-13 wt % ZrO2, where amount TiO2 and/or SnO2 and/or ZrO2 = 1% above amt. required to form Bi2 (TiO3)3 and/or Bi2 (SnO3)3 and/or Bi2(ZRO3)3; or constits capable of forming these cpds. (2) pressing to desired shape, rolling or casting and opt. cutting or punching and (3) sinter-scaling at 1150-1250 degrees C, opt. after drying. Pref. raw materials consist at least in part of previously prepd. titanates and/or stannates, more pref. 72-5 wt % BaTiO3, 14.2 wt % BaSnO3 and 13.3. wt % Bi2 (TiO3)3, and opt. 0.5-3 wt %CeO2, 0.5-3 wt % Nb2O5, esp. added as KNbO3. One or more organic plasticisers may be added.

Description

Process for the production of a ceramic dielectric.

The present invention relates to a method of manufacture a ceramic dielectric with a dielectric constant of about 700 until 2000 based on barium titanate and barium stannate.

In the case of ceramic dielectrics, there is more and more demand that their electrical and mechanical properties depend on the individual operating states such as voltage, frequency, temperature, operating time only change very little.

A ceramic dielectric based on barium titanate and barium stannate is known from German patent specification 909 819. However, this has in one If in a temperature range from 20 0C to 130 0C a £ value between 3580 and 8950 and in a second case listed in a table with the specified Temperatures have an s value between 7720 and 1940. This reference also gives no references to the other properties, such as long-term behavior in particular with and without operating voltage, DC voltage dependence of the capacitance on the Frequency and dielectric strength.

The object of the invention is to be achieved, a dielectric with a g of around 700 to 2000 that can withstand high stresses, and over a very long period of time, while maintaining the c-value as much as possible remain. In addition, the insulation resistance and the loss factor should also be high Temperatures remain constant if possible.

According to the invention, this object is achieved in that the oxides of barium, tin, titanium and bismuth corresponding to a final composition of 55 - 85 wt .-% BaTiO3, 5-20 wt .-% BaSn03 and 0.5-5 wt .-% Bi203 and / or one Addition of a mixture of Bi203 and DiO2 and / or 51102 and / or ZrO2 with the proportions of the individual additions of 1.2 - 20 wt .-, ° S Bi203, 0.6 - 10 'TiO2, o, 9-15 'Sn02, 0.8-13 ZrO2, whereby the proportion of Ti02 and / or SnO2 and / or ZrO2 at most 1 io above that for the formation of Bi2 (Ti03) 3 and / or Bi2 (SnO3) 3 and / or Bi2 (ZrO3)) is the required amount or components that these compounds able to form, mixed, then pressed into the desired shape, rolled or cast and then, if necessary, cut or punched and then, if necessary, after a drying process, are densely sintered at 1150 to 12500C.

As a particularly favorable composition for a dielectric with a required 6 out of approx. 1000 and the desired good properties the following mixture was shown: 72.5% by weight of BaTiO3, 14.2% by weight of BaSnO3 and 13.3 wt .-, ó Bi2 (TiO3) 3 with the addition of methyl cellulose and / or similar organic compounds with plasticizing properties as plasticizers intimately measured, then by pressing under a pressure of approx. 2 t / cm2 body In platelet, disc or tube shape or the like. Manufactured after a Drying at approx. 600C within approx. 4 hours heated to 12000C and 1 hour on this temperature were maintained. It was then slowly brought to room temperature in about 12 hours cooled down. The densely sintered ceramic bodies were placed on the opposite Pages silver-plated in the conventional way.

The ceramic bodies produced in this way had a £ value of about 1000, a DC voltage dependency of less than 2% at a field strength between zero and 1000 V / mm, a £ value decrease of less than 6% after 10,000 hours at an operating voltage of 40O Usual storage and operating temperatures up to 1 250C and an insulation resistance of approx. 105 M, which increases with the temperature; and with an even smaller tg ö at a higher temperature. The temperature dependence of 6 was between -40 ° C and + 1250C with 1 Idiz less than 10, b. The breakdown voltage .tClSt something with the temperature.

For the production of the ceramic dielectric, there are options the or some prefabricated titanates and the stannate also the starting products, So BaO e.g. as BaC03, TiO2, Sn02, Bi203 or other compounds that have the desired Composition of the ceramic according to the invention, find use. Included it may be useful to carry out an intermediate firing to finely age the product and then manufacture the end product from this.

Based on the drawing, the electrical properties are in the diagrams graphically represented.

Slight additional improvements in the properties achieved occur still on if the ceramic contains about 0.5-3% by weight CeO2 and / or 0.5-3% by weight Nb205, optionally be added as potassium niobate.

The same applies if bismuth oxide (BioO) is also in unbound Form is present in the dielectric.

With a corresponding change in the composition of the invention specified compounds within the specified limits, changes in the dielectric constant occur from a maximum of 10% to with long-term behavior, e.g. during storage and permanent load.

The tg # remains within the limits of about 1.10-³ to 15.10.

Disks, tubes, Platelets or blocks etc. can be pressed or foils can be rolled or cast which can then be cut to the desired shape.

Stack capacitors, e.g. through Spread with electrode pastes that can withstand the firing temperature.

Claims (8)

Patent claims: A method for producing a ceramic dielectric having a Dielectric constants of about 700 to 2000 based on barium titanate and Barium stannate, characterized in that the oxides of barium, tin, titanium and Bismuth corresponding to a final composition of 55 - 85% by weight BaTiO3, 5 - 20% by weight BaSn03 and 0.5-5% by weight Bi203 and / or an addition of a mixture of Bi203 and Ti02 and / or SnO2 and / or Zero2 with the proportions of the individual additives of 1.2 - 20 wt .- / o Bs203, 0.6-10 'DiO2 0.9-15' In02 '0.8-13' Zr02 where the proportion of TiO2 and / or SnO2 and / or ZrO2 at most 1 /% above that for the formation of Bi2 (TiO3) 3 and / or Bi2 (SnO3) 3 and / or Bi2 (ZrO3) 3 is the required amount, or components, capable of forming these compounds, mixed, then into the desired Molded, rolled or cast and then cut if necessary or punched and then, optionally after a drying process, at 1150 to 1250 ° C be densely sintered. 2. The method according to claim 1, characterized in that the starting raw materials at least some of the prefabricated titanates and / or stannates are used. 3. Process for the production of a ceramic dielectric according to Claim 1 or 2, characterized with a dielectric constant of approximately 1000 by using raw materials according to a final composition of 72.5% by weight BaTiO3, 14.2% by weight BaSnO3 and 13.3% by weight Bi2 (TiO3) 3. 4. The method according to at least one of claims 1 to 3, characterized by adding 0.5-3% by weight CeO2. 5. The method according to at least one of claims 1 to 4, characterized by adding 0.5-3% by weight of Nb205. 6. The method according to claim 5, characterized in that Nb205 in Form of KNbO3 is used. 7. The method according to at least one of claims 1 to 6, characterized in that that the approach in a known manner one or more organic plasticizers can be added. 8. Electrical capacitor characterized by the use of a Dielectric produced according to the method according to at least one of Claims 1 to 7. Blank page