The dependence of sintering temperature on Schottky barrier and bulk electron traps of ZnO varistors

In order to investigate the influence of sintering temperature on the Schottky barrier and bulk electron traps of ZnO varistors, ZnO-Bi2O3 based varistor ceramic samples were sintered at 1000, 1100, 1200 and 1300°C, respectively. The measured results indicate that the sample sintered at 1300°C possesses the lowest voltage gradient and nonlinear coefficient, compared with other samples. The barrier height of the samples decreased as the sintering temperature increased, which resulted in the deterioration of nonlinearity. Furthermore, two bulk electron traps determined by admittance spectroscopy were generally independent of sintering temperature, which indicated that these two traps might originate from the intrinsic defects in ZnO lattice.