Effect of Sintering Temperature on Electrical Properties of ZnO Varistor Ceramics

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135 similar to 1155 degrees C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 degrees C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8 mu A and the density is 96.4%. When the sintering temperature is at 1140 degrees C, the voltage gradient of varistor is 301V/mm, the leakage current is 4 mu A and the density is 96.6%. Compared the results at 1135 degrees C with 1140 degrees C, it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 degrees C.