The low-voltage varistor was made by seed grain method at various sintering conditions such as sintering time and sintering temperature. The microstructure and electrical properties were investigated and compared with those of the varistor made by conventional method.
The added seed grain rapidly grew to be a giant grain, which gave easy path to current flow. Therefore the breakdown voltage was lowered as much as the order of 1/10-1/5 in comparison to that of the varistor made by conventional method. But the size of the giant grain was little influenced by sintering condition, so the breakdown voltage was little changed.
The weight loss was decreased by the addition of the seed grain, because the giant grain decreased the evaporation area. Therefore the nonohmic property of the varistor made by seed grain method was little influenced by sintering condition. In this experiment the low-voltage varistor made by seed grain method showed the least leakage current when sintered at 1150℃ for zero hour.
