JPH02184568A - Porcelain composition for voltage-nonlinear resistance element - Google Patents

Abstract

PURPOSE:To obtain the subject porcelain composition having a high voltage- nonlinear coefficient, a high resistance to surging and a small change thereof with time by mixing a specified oxidizing agent into a specified semiconductive porcelain consisting of an Sr-Ca-Ti-O-based compound as the main component. CONSTITUTION:An objective porcelain composition prepared by mixing a semiconductive porcelain composed of 98.0-99.9mol% formula l (0<=x<=0.25; 0.996<=y<=1.003) and 0.1-2.0mol% oxide of Nb, W, Ta, In, Y or a rare earth element with 0.01-2.0wt.% formula II (M is one or more of monovalent metallic element; Y>1). By using the above-mentioned composition, the subject porcelain composition for a voltage-nonlinear resistance element having an excellent resistance to surging after application of 5000A/cm<2> surge voltage, a high nonlinear coefficient (alpha) higher than 15 and a small change of dielectric loss with time under high temperatures and high humidity, i.e. excellent in humidity- resistant properties is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a ceramic composition for obtaining a voltage nonlinear resistor containing (Sr+-xca+t)TiyOs as a main component.

<Prior art and its problems> Various varistors are used to absorb or remove abnormal voltages, noise, etc. generated in electronic devices.

In a grain boundary oxidation type voltage nonlinear resistance element, varistor characteristics are obtained by oxidizing the grain boundaries. As oxidation methods, air oxidation or grain boundary diffusion of oxides such as NaaO are known, but the former method generally results in poor varistor characteristics (and the latter method results in poor capacitance). Although it may be possible to satisfy any of the following characteristics, such as a large size, a large nonlinear coefficient (α), or a large surge resistance, it is impossible to satisfy all of these characteristics with a single composition. There was nothing to do.

A voltage nonlinear resistor whose main component is strontium titanate functions not only as a varistor that absorbs abnormal voltage and noise, but also as a capacitor.

Examples of this type of material include SrTi0m or Sr+-xCaxTiOs, as disclosed in Japanese Patent Application Laid-Open No. 58-16504 and Japanese Patent Application Laid-open No. 58-91602.
(0,01≦x≦0.5) as the main component, and Nb*Os, Ta1ls,
WOs, La1es, Cent, Nd! O,,Y2
Metal oxides such as O, and N to prevent surge deterioration
It consists of something containing a1O.

However, even with these compositions, although a large nonlinear coefficient α can be obtained, it is not possible to obtain a structure with small deterioration of α and varistor voltage even when a surge is applied.

<Object of the invention> In view of the above, this invention has an arbitrary varistor voltage,
Another object of the present invention is to provide a ceramic composition for a voltage nonlinear resistor, which has characteristics of a high nonlinear coefficient (α) and high surge resistance, and has little change in these characteristics over time.

<Means for Solving the Problems> That is, this invention was made to solve the above-mentioned problems, and (Sr+-xcax) Tiy Os (provided that 2O≦x
≦0, 25.0, 996≦y≦1.003) is 98.
0 to 99.9 mol%, Nbs Ws Ta-In, Y
Alternatively, semiconductor porcelain consisting of 0.1 to 2.0 mol% of rare earth element oxides may be made of MJ/YSiOt (where M is a small amount of monovalent metal elements (both are 1 type and Y is greater than 1) and is 0. The present invention provides a ceramic composition for a voltage nonlinear resistor containing .01 to 2.0% by weight.

(Sr+-xCa,)T used as the main component in this invention
i.

In 03, the reason why the amount of y is set in the range of 0.996 to 1.003 is that the surge resistance is improved when y is in the range of less than 1.000 to 0.996, whereas the surge resistance is improved when y is in the range of 1.000 to 1.0.
This is because within the range of 0.03, the characteristics are stable and variations are reduced.

Furthermore, in (Sr+-xCaJ TiyO5, X is set to 0≦x≦0.25 because if the Ca amount exceeds 0.25, the surge resistance decreases, which is not preferable.
The reason why the amount of Nb%W, Ta%In, Y or rare earth element oxide as a semiconductor agent is set to 0.1 to 2.0 mol% is because these oxides do not exhibit Baritas characteristics at 0 mol%. , when it exceeds 2.0 mol%, the surge resistance decreases.

Further, when the amount of the compound represented by M2O.Y 5if2 used as an oxidizing agent becomes 0.01% by weight, the varistor voltage and nonlinear coefficient decrease, and when it exceeds 2.0% by weight, the surge resistance decreases.

<Example> The present invention will be explained in detail below with reference to Examples.

SrC0m, 'riOa, Ca01 were used as the base material and the semiconducting agent so as to have the composition ratio (mol%) shown in Table 1.
The raw material powders of Y203, Lag's, and Era's were weighed, blended, mixed wet, and dried at 1150°C.
It was calcined for 2 hours.

After pulverization, the granules obtained by adding 5% by weight of vinyl acetate resin were pulverized to a diameter of 10 m at a pressure of 1 ton/cm.
It was molded into a pellet having a thickness of 1.5 mm.

The obtained molded body was fired in air at 11000°C for 2 hours, and then fired at 1450°C for 2 hours in a mixed gas atmosphere of H-/Ni=1/loo (vol ratio) to obtain semiconductor porcelain.

The alkali silicate shown in Table 1 was applied to the surface of the obtained semiconductor ceramic in an amount of 0.5% by weight based on the weight of the unit material, and heat treated in air at 1200° C. for 2 hours.

A voltage nonlinear resistor element was obtained by providing a silver electrode on the facing surface of the ceramic unit thus obtained, and the varistor voltage V1% nonlinear coefficient α of the element, the rate of change of ■1 and α due to the application of a surge voltage Δ■ When the electrical characteristics such as + and Δα were investigated, the results shown in Table 1 were obtained.

In addition, sample fish in the table marked with * are outside the scope of the claims of this invention.

In addition, the voltage nonlinear resistance element of the present invention obtained with Sample No. 2 in Table 1 and Sro, 5ocao, *oT
iOs, 99.0 mol%, Y2O. 0.5 mol%, Na
A conventional voltage nonlinear resistance element consisting of 5 mol % of zQO was left at 60°C and a relative humidity (R)I) of 95%,
When the change in dielectric loss in the vortex over time was investigated, the results shown in FIG. 1 were obtained, and it was recognized that the ceramic composition of the present invention has excellent moisture resistance at high temperatures.

<Effects of the Invention> As explained above, according to this invention, 5000A/c
It has excellent surge resistance after applying a surge voltage of m'', has a high non-linear coefficient (α) of α>15, and has small changes in dielectric loss over time in high temperature and high humidity, that is, has excellent moisture resistance. A ceramic composition for a voltage nonlinear resistor is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the change over time in dielectric loss of a voltage nonlinear resistor using the ceramic composition of the present invention at high temperatures.

Claims (1)

[Claims] (Sr_1_-_xCa_x)Ti_yO_3 (However,
0≦x≦0.25, 0.996≦y≦1.003) is 9
8.0 to 99.9 mol%, Nb, W, Ta, In, Y
Alternatively, M_2O・YSiO_2 (however, M_2O・YSiO_2
A ceramic composition for a voltage nonlinear resistor, which contains 0.01 to 2.0% by weight of at least one monovalent metal element, and Y is greater than 1.