Effect of sintering temperature on microstructure and electrical properties of Zn·Pr·Co·Cr·La oxide-based varistors

The microstructure and electrical properties of varistors, which are composed of Zn·Pr·Co·Cr·La oxide-based ceramics, were investigated with different sintering temperatures. The increase of sintering temperature led to more densified ceramics, whereas it decreased the varistor voltage and nonlinear properties. The highest nonlinearity was obtained from 1230 °C, with 77.9 in nonlinear exponent and 0.4 μA in leakage current. As the sintering temperature increased, the donor concentration and density of interface states increased in the range of 0.90 × 1018 to 2.59 × 1018/cm3 and 3.98 × 1012 to 4.04 × 1012/cm2, respectively. The barrier height decreased with increasing sintering temperature, reaching a minimum (0.67 eV) at 1300 °C.