High nonlinearity in 0.1 mol.% In2O3 added ZnO–V2O5 based varistors prepared at different sintering temperatures

Abstract

High-performance ZnO-V2O5 based varistors doped with 0.1 mol.% In2O3 have been prepared via conventional sintering method at 850–925 °C. Experimental results show that indium doping helps to improve the nonlinear exponent (α), breakdown field (Eb) of the developed varistors. Added In2O3 restricts the grain growth in the ZnO ceramics, which in turn, causes an increase in the breakdown potential of the varistor samples. High nonlinearity (α > 100) has been obtained consistently in the developed varistors at all the sintering temperatures (850–900 °C). Doped In3+ ions appear as a donor at the grain boundaries, leading to an increase in the Schottky barrier height. The comparatively high leakage current density in ZnO–V2O5 based varistors (usually >100 μA cm−2) could be restricted within 62–83 μA cm−2 in these samples. The sample sintered at 875 °C resulted in a dense (98% TD) fine-grained (1.1 ± 0.1 μm) varistor showing optimum electrical properties with Eb value of 14.2 kV cm−1, α value of 153, and JL equals to 62 μA cm−2.