<i>I-V</i> Characteristics of Single Grain Boundary in ZnO Varistor

Abstract

I (current)-V (voltage) characteristics of single grain boundaries in ZnO varistor were directly measured by D. C. four-point probe method using a constructed instrument. The I-V characteristics of single grain boundaries were different at each grain boundary and classified into three patterns. The resistance of the grain boundary phase seemed to affect the I-V characteristics of the grain boundary. Non-linear coefficients of single grain boundaries were in the range of 2 to 100 and their average value was 14.8, in good agreement with that of the sintered body. The breakdown voltage of single grain boundaries also varied widely between 1.5-5V with an average value of 3.3V. The breakdown voltage of a single grain boundary calculated from that of the sintered body was 1.88V. One of the factors affecting the difference between the measured and calculated value of the breakdown voltage was considered to be the difference in the measuring current density.