Evolution of Intrinsic Defects Concentration of ZnO Varistor Ceramics Doped with Ni2O3 during Sintering

Precisely manipulating the intrinsic defects is the key to obtain superior anti-aging properties in ZnO varistor ceramics. To achieve this goal, it is fundamental to understand the evolution of intrinsic defects concentration of ZnO varistors during sintering. Thus, in this study, ZnO varistor ceramics doped with and without Ni2O3 were prepared via the solid-state method. To record the intrinsic defects concentration during sintering, samples were quenched at various temperatures of 350°C, 500°C, 600°C, and 700°C. Results showed that as the quenching temperature decreased, the nonlinear coefficient of the undoped ZnO samples gradually increased. Besides, when the undoped ZnO samples were quenched at high temperature, the zinc interstitials concentration and oxygen vacancies concentration were little, but the intrinsic defects concentration of the ZnO samples after the entire sintering process was greatly increased. The intrinsic defects concentration value of the doped ZnO samples was generally greater than that of the samples undoped ZnO samples, and the reverse manipulation of intrinsic defects occurred in the process of doped ZnO quenched from high temperature to low temperature, that is, zinc interstitials concentration increased and the oxygen vacancies concentration decreased.