Nonlinear Property of (Nb 2 O 5 , Sr CO 3 , Ge, GeO 2 )‐Codoped TiO 2 ‐Based Varistor Ceramics

This study investigated the influence of codoping with Ge and GeO 2 on the nonlinear coefficient α and the breakdown voltage E B of TiO 2 –Nb 2 O 5 –SrCO 3 varistor ceramics. Ge–GeO 2 codoping notably changed the microstructure of the TiO 2 –Nb 2 O 5 –SrCO 3 ceramics, increased α, and decreased E B . When the doping contents of Nb 2 O 5 and SrCO 3 were 0.1 and 0.2 mol%, respectively, the optimum doping content of 0.25 mol% Ge and 0.75 mol% GeO 2 exhibited high α (11.6), low E B (13.8 V/mm), and high grain‐boundary barrier Φ B (0.96 eV). These results are superior to previous findings. In addition, Ge and GeO 2 , which function as sintering aids, reduced the sintering temperature caused by the low melting point. The optimal sintering temperature was 1260°C for the TiO 2 –Nb 2 O 5 –Sr CO 3 ceramics doped with Ge and GeO 2 .