JPH0247089B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ceramic composition for a voltage non-linear resistor, and particularly to a strontium titanate-based ceramic composition for a voltage non-linear resistor having high anti-deposition strength. (Prior Art) It is known that a voltage nonlinear resistor (hereinafter referred to as "varistor") can be obtained by increasing the resistance of the grain boundaries of strontium titanate-based semiconductor ceramics.
Are known. An application of this type of varistor is a ring varistor for absorbing sparks in micro motors. This ring varistor is usually mounted as is without being covered with a resin dip or the like, so it is required to have high anti-destructive strength. In particular, varistors used in micro motors and the like are small, so high anti-destructive strength is required as an important characteristic. (Problems to be Solved by the Invention) Conventional varistors made of strontium titanate-based semiconductor ceramics have low anti-destructive strength, and therefore the wall thickness must be approximately 1 mm. It was not suitable as a varistor for a motor. Therefore, the main object of the present invention is to provide a porcelain composition for a varistor that has good varistor properties and a high anti-destructive strength. (Means for Solving the Problems) The present invention provides strontium titanate or strontium titanate containing other titanates, zirconates, and stannates.
The main components are 98.80-99.88 mol%, _{Er2O3 and}
At least one of Ho ₂ O ₃ and Ta ₂ O ₅ and
The total of at least one of Nb ₂ O ₅ is 0.1 to 1.0
This is a ceramic composition for a voltage nonlinear resistor, in which _MnO2 is 0.02 to 0.2 mol%, the crystal grains of the ceramic are semiconductor, and the crystal grain boundaries are made highly resistive. (Effects of the Invention) According to the present invention, an excellent porcelain composition for a varistor having a nonlinear coefficient (α) of 7.5 or more and a resistive strength of 2.5 Kg or more can be obtained. The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. (Example) Each powder of SrTiO ₃ , CaTiO ₃ , BaZrO ₃ and BaSnO ₃ which is the main component, and Er ₂ O ₃ which is a semiconducting agent,
Each powder of Ho ₂ O ₃ , Ta ₂ O ₅ and Nb ₂ O ₅ was
The mixture was weighed, 3 to 10% by weight of binder was added, and wet pulverized in a polypot for about 10 hours so as to obtain porcelain having the composition ratio shown in the table. After dehydrating, saran sieve 50
The particles were sized using a mesh and formed into a ring shape with an outer diameter of 13.5 mm, an inner diameter of 8 mm, and a wall thickness of 1.2 mm. Then 1100
Pre-calcined for 1 hour at ℃, followed by nitrogen 97
% and 3% hydrogen at 1380° C. for 2 hours. The outer diameter of fired porcelain is 11mm.
The inner diameter was 6.6 mm and the wall thickness was 1 mm. Furthermore, three silver electrodes were formed on one side of the ring-shaped porcelain with a gap of 1.5 mm, and a silver electrode was formed on the entire surface of the other side to prepare a sample. In the varistor obtained in this way, the crystal grains of the porcelain are semiconductors, and the crystal grain boundaries of the porcelain have a high resistance. The obtained sample was connected to a constant current power supply, and the voltage values at 1 mA and 10 mA were measured.
The voltage values at that time were determined as E1 and E10, respectively. And the threshold voltage (Vth) is E10
The nonlinear coefficient (α) was determined using the following formula. α=1/(logE10/E1) In addition, the anti-deposition height is determined using a push-pull gauge.As shown in the drawing, the lower surface of sample A is supported by supports B and C, and the upper surface of sample A is measured by supports B and C. A static load (W) is applied in the direction of the arrow in the drawing by the cutting edge D approximately in the middle of C, and the static load is expressed as the static load when sample A breaks. The measurement results are shown in Table 1. Note that the anti-destructive strength indicates a value on the verge of the sample breaking. The samples marked with * in Table 1 are outside the scope of this invention, and all other samples are within the scope of this invention.

【table】

[Table] Comparative example Main component SrTiO ₃ and semiconducting agent
Y ₂ O ₃ , Nb ₂ O ₅ , WO ₃ , La ₂ O ₃ and the like were weighed so as to obtain porcelain having the composition shown in Table 2, and then treated in the same manner as in the Examples to obtain samples. The threshold voltage (Vth), nonlinear coefficient (α), and anti-deposition strength (Kg) of the obtained sample were measured in the same manner as in the examples, and the results are shown in Table 2.

[Table] As is clear from comparing Tables 1 and 2,
As in this invention, Er ₂ O ₃ ,
By containing at least one type of H ₂ O ₃ and at least one type of Ta ₂ O ₅ and Nb ₂ O ₅ , the threshold voltage and nonlinear coefficient are inferior to conventional ones in terms of characteristics. Moreover, we were able to improve the anti-destructive strength by about 20 to 80%.

[Brief explanation of the drawing]

The drawing is a schematic diagram illustrating a method of measuring anti-resistance strength.

Claims (1)

[Claims] 1. Strontium titanate, or other titanates based on strontium titanate,
The main components include zirconate and stannate.
98.80 to 99.88 mol%, with at least one of Er ₂ O ₃ and Ho ₂ O ₃
The total amount of at least one of Ta ₂ O ₅ and Nb ₂ O ₅ is 0.1 to 1.0 mol %, MnO ₂ is 0.02 to 0.2 mol %, and the crystal grains of the porcelain are semiconductors and the grain boundaries are high. A ceramic composition for a voltage nonlinear resistor that is made into a resistor.