Tailoring electrical properties of multiple dopant-based ZnO varistor by doping with yttrium, gallium, and indium

Abstract We performed SEM, electric field-current density measurements, capacitance-voltage testing, and X-ray diffraction analysis to study the effects of indium doping on the microstructure and electrical properties of ZnO varistors co-doped with Ga2O3 and Y2O3. Our results showed that the residual voltage ratio of the sintered samples decreased with the introduction of indium at defined aluminum and yttrium content. The introduction of indium clearly improved the nonlinear coefficient. The ZnO varistor samples showed optimal performance at a composition of 0.025 mol% indium, 0.4 mol% gallium, and 0.9 mol% yttrium. This sample exhibited a residual voltage ratio of 1.45, a nonlinear coefficient of 76.2, a 1-mA residual voltage of 454 V/mm, and a leakage current of 1.44 µA/cm2.