Effect of sintering temperature and Ho2O3 on the properties of TiO2-based varistors

Abstract

In this study, a series of TiO2-based ceramics doped with different contents of Ho2O3 in the range of 0–0.6 mol% are prepared by means of a conventional solid-state reaction method. Phase composition, microstructure and element distribution are studied by use of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) separately. The influence of sintering temperature and Ho2O3 on the properties of samples is explored. The results show that the breakdown voltage decreases continuously while both the nonlinear coefficient and the relative dielectric constant ascend firstly and then descend with the sintering temperature increasing. Meanwhile, the relative dielectric constant and nonlinear coefficient of samples firstly ascend and then descend with the increasing of Ho2O3. Although the minimum breakdown voltage (3.3 V/mm) is obtained when sample is sintered at 1450 °C, the sample doped with 0.45 mol% Ho2O3 sintered at 1400 °C exhibits high comprehensive electrical properties, with breakdown voltage of 6 V/mm, the nonlinear coefficient of 5.5 and the relative dielectric constant of 1.88 × 105.