Effects of Grain-Size Distribution on the Breakdown Voltage in ZnO Varistors

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J. Korean Ceram. Soc. > Volume 30(3); 1993 > Article

Journal of the Korean Ceramic Society 1993;30(3): 199.

입도분포가 ZnO 바리스터의 임계전압에 미치는 영향

김경남, 한상목, 김대수¹

강원대학교 재료공학과
¹삼척산업대학 재료공학과

Effects of Grain-Size Distribution on the Breakdown Voltage in ZnO Varistors

ABSTRACT

Effects of grain size distribution on the breakdown voltage of ZnO varistors were investigated in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems, respectively. The grain size was increased with increasing sintering temperature maintaining lognormal distribution in both systems. The width of grain size distribution of ZnO-Bi2O3-CoO-Sb2O3 system was narrower than that of ZnO-Bi2O3-CoO-Sb2O3 system. The breakdown voltage(Vb) was decreased by increasing sintering temperature(1000~135$0^{circ}C$) and sintering time(0.5~5hr), due to the enhancement of ZnO grain growth. The current path of the ZnO varistor was dependent on the distribution of the largest grains (chains of long grains) between the electrodes.