Ge-added TiO2–Ta2O5–CaCO3 varistor ceramics.

The influence of doping with Ge on the nonlinear coefficient α and the breakdown electric field E B of TiO 2 –Ta 2 O 5 –CaCO 3 varistor ceramics was investigated. In this study, TiO 2 –Ta 2 O 5 –CaCO 3 varistor ceramics added with Ge was successfully prepared using the traditional method of ball milling–molding–sintering. The electrical performance, including the nonlinear coefficient α , the breakdown electric field E B , and the leakage current J L , are tested using a varistor direct current parameter instrument. The average barrier height Φ B of each sample is calculated using the relevant formula. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning transmission electronic microscopy analyses demonstrated that Ge doping notably changed the microstructure of TiO 2 –Ta 2 O 5 –CaCO 3 ceramics, thereby increasing α and decreasing E B . When the doping contents of Ta 2 O 5 and CaCO 3 were 0.2 and 0.4 mol%, respectively, the optimum doping content of 0.9 mol% Ge exhibited high α (10.2), low E B (14.1 V mm −1 ), and high Φ B (0.95 eV). These results are superior to previous findings. In addition, Ge as sintering aid reduced the sintering temperature caused by the low melting point. The optimal sintering temperature was 1300 °C for the TiO 2 –Ta 2 O 5 –CaCO 3 ceramics doped with Ge. [ABSTRACT FROM AUTHOR]