Effect of SnO2 doping on microstructural and electrical properties of ZnO-Pr6O11 based varistor ceramics

Highlights: → ZnO-Pr6O11 based varistor ceramic materials → Eliminating the few drawbacks due to the high volatility and reactivity of Bi2O3 during liquid sintering by Pr6O11 substituting Bi2O3 → Doping effect of SnO2 on ZnO-Pr6O11 based varistor ceramic materials → Optimizing doping of SnO2 in ZnO-Pr6O11 based varistor ceramic materials. - Abstract: ZnO-Pr6O11 based varistor ceramics doped with 0-2.0 mol% SnO2 were fabricated by sintering samples at 1300 deg. C for 2 h with conventional ceramic processing method. X-ray diffraction analysis indicated that the doped SnO2 reacted with praseodymium oxides during sintering, generating Pr2Sn2O7 phase. Through scanning electron microscopy, it was found that the doping of SnO2 played a role against the growth of ZnO grains. Capacitance-voltage analysis revealed that the doped SnO2 acted as a donor in the varistor. The measured electric-field/current-density characteristics of the samples showed that the varistor voltage increased with the increase of SnO2 doping content, when the SnO2 content was no more than 1.0 mol%; with the SnO2 content up to no more than 0.5 mol%, the doping of SnO2 could increase the nonlinear coefficient; but, when the SnO2 doping content was further increased, the nonlinear coefficient and varistor voltage of the samples decreased, and the leakage current increased.