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

•About 0.1 mol.% of Cr2O3 is optimal for the formation of the increased electrostatic double Schottky barriers height and thus an enhanced coefficient of nonlinearity α = 74 and a lower leakage current (IL < 0.2 μA/cm2).•Small amounts of added Cr2O3 primarily result in the formation of acceptor defects at the GBs for enhanced electrostatic Schottky barriers, which leads to an enhanced current-voltage (I-V) nonlinearity and a decrease of the leakage current.•For larger additions of Cr2O3 (above 0.20 mol.%) the Ca3(CrO4)2 phase starts to form, which led to a decreased barrier height and thus a decreased I-V nonlinearity with an α value of 25 and an increased leakage current (IL > 5 mA/cm2).