Microstructure and electrical properties of Y₂O₃-doped ZnO-based varistor ceramics prepared by high-energy ball milling

Y₂O₃-doped ZnO-based varistor ceramics were prepared using high-energy ball milling (HEBM) and low-temperature sintering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm³. With increasing Y₂O₃ content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor concentration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y₂O₃ in varistor ceramics.