Tailoring low leakage current and high nonlinear coefficient of a Y-doped ZnO varistor by indium doping

Abstract

The present study focuses on the effect of indium doping on the microstructure and electrical properties of Y-doped ZnO varistor ceramics. At a given concentration of the rare-earth element yttrium, the leakage currents of sintered varistors first decreased markedly with increased indium doping, before increasing at higher doping levels. The nonlinear coefficient showed the opposite trend. A fraction of the doped In3+ ions dissolved into the grains and caused the grain resistance to decrease, leading to a low level residual voltage. The In3+ ions present at the grain boundaries increased the barrier height, and further inhibited increases in the leakage current. When doped with 0.025mol% indium and 0.9mol% yttrium, the sintered varistors showed optimal electrical properties with a leakage current of 4.15 μA/cm2, nonlinear coefficient of 51.84, residual voltage ratio of 1.61, and voltage gradient of 615.59V/mm.