Effect of co-doping Y_2O_3-La_2O_3 on microstructure and electrical properties of ZnO-based varistor ceramics prepared from nanosize ZnO powder

摘要

AbstractZnO-based varistor ceramics doped with fixed La2O3and different Y2O3have been fabricated by the conventional solid-state reaction route. Phase composition, microstructure, and electrical properties were studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and direct current electrical measurement. The Y2O3phase, Y-rich phase and La-rich phase were found to distribute along the grain boundaries of predominant ZnO grains from XRD and SEM analyses. The average grain size of the primary phases was calculated to be in the range of 3.80 to 4.17 μm. The varistor ceramic doped with 0.1 mol% La2O3and 0.5 mol% Y2O3sintered at 1100 °C for 2 h exhibited high comprehensive electrical properties with the breakdown field of 1055 V/mm, the nonlinear coefficient of 65.5 and the leakage current of 0.6 μA. The results illustrated that co-doping La2O3and Y2O3and employing the ZnO powder in nanometer size may be a promising route to obtain varistor ceramics with excellent electrical properties.