Effect of La2O3 Dopant on Microstructure and Electrical Nonlinearity of ZnO-CaMnO3 Based Varistor Ceramics

In this research, zinc oxide based varistor are produce by using citrate-gel method compared to conventional solid-state method. The zinc oxide based varistor are fabricate using three different wt.% of ZnO-CaMnO3-La2O3 and divided into three system which are 80 mol% ZnO + 20 mol% CaMnO3, 79.5 mol% ZnO + 20 mol% CaMnO3 + 0.5 mol% La2O3 and 78.5 mol% ZnO + 20 mol% CaMnO3 + 1.5 mol% La2O3. ZnO-CaMnO3-La2O3 compound experienced pre-sintering at 500 °C for 2 hours sintering time. In the sintering condition, sintering temperatures are manipulated, which are varied at 1100, 1200 and 1300 °C while, the sintering time is setting at 4.5 hours. X-ray diffraction patterns show this compound is high in crystallinity. The surface morphology with the average grains size between 2.0 ∼ 10.0 μm was observed by Scanning Electron Microscopy. Energy Dispersive Spectroscopy confirmed that distribution of element are homogenous with high purity. Density of the sample product is range between 5.0 ∼ 5.6 g cm−3. J-E characteristic shows the value of non-linearity coefficient in the range of 1.10 to 4.35.