Effect of Sr Doping on Nonlinear Current–Voltage Properties of ZnO-Based Ceramics

SrCO 3 was used as a nonlinear-forming additive for ZnO-based ceramics. The Sr-doped ZnO ceramics were synthesized by the conventional solid-state method and their performance was studied systematically. The Sr-doped samples showed nonlinear current-voltage properties with a max nonlinear coefficient of 6.26. The structural and morphological characterizations pinpointed the formation of the intergranular phase, which was related to the segregation of Sr at the grain boundary. The electrical modulus spectra and impedance spectra were interpreted by the relaxation behaviours correlated with the grain boundary effect and oxygen vacancies. Meanwhile, the increase of the grain boundary resistance was also ascribed to the influence of Sr doping. These detailed studies demonstrated the potential of Sr-doped ZnO ceramics and provided a guidance to prepare a bismuth-free ZnO-based varistor.