Influence of Cr2O3 doping on the electrical characteristics of novel ZnO-Cr2O3-based varistor ceramics

Novel ZnO-Cr2O3-based varistors can overcome the problems related to the volatile, high-cost and toxic com-ponents of conventional ZnO-Bi2O3-, ZnO-Pr6O11-, and ZnO-V2O5-based varistors. The influence of the varistor former with different doping levels, i.e., the Cr2O3, on the microstructure and electrical properties was examined and the optimal amount of Cr2O3 doping to enhance the electrical performance of ZnO-Cr2O3-based varistor ceramics was determined. The results showed that about 0.1 mol.% of Cr2O3 is optimal for the formation of the electrostatic double Schottky barriers with increased height at the grain boundaries (GBs) and thus an enhanced I -V nonlinearity (i.e., a coefficient of nonlinearity alpha = 73) and a lower leakage current (IL < 0.2 mu A/cm2) in ZnO-Cr2O3-based varistor ceramics with an Eb of 383 V/mm. For larger additions of Cr2O3, a Ca3(CrO4)2 phase forms, which decreases the barrier height and leads to a lowering of alpha and an increase in IL.

Automated summary

Novel ZnO-Cr2O3-based varistors can solve the issues related to volatile, high-cost and toxic components in traditional ZnO-Bi2O3, ZnO-Pr6O11, and ZnO-V2O5-based varistors. The influence of different doping levels of Cr2O3 on the microstructure and electrical properties of varistors was studied, and the optimal amount of Cr2O3 doping to enhance the electrical performance was determined. The results showed that 0.1 mol.% of Cr2O3 is optimal for obtaining improved electrical properties, with increased nonlinearity coefficient (alpha = 73) and lower leakage current (IL < 0.2 mu A/cm2) in ZnO-Cr2O3-based varistors at an applied electric field of 383 V/mm. Larger additions of Cr2O3 lead to the formation of a Ca3(CrO4)2 phase, causing a decrease in barrier height, lower alpha and increased IL.