Influence of Sm2O3 on electrical performance of (Nb, Si)-doped TiO2-based varistor

Abstract

In this work, TiO 2 -based varistor ceramics doped with Nb 2 O 5 , SiO 2 and Sm 2 O 3 are prepared by using conventional solid state synthesis. X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometer and direct current electrical measurement are used to study phase composition, microstructure and nonlinear properties. It is found that the second phase emerges at grain boundary, having a great influence on nonlinear electrical behaviors. Breakdown voltage E 1mA initially decreases and then increases with increasing of Sm 2 O 3 content. The minimum of breakdown voltage E 1mA (9.3 V/mm) occurs at the composition of 99.0 %TiO 2 -0.5 %Nb 2 O 5 -0.3 %SiO 2 -0.2 %Sm 2 O 3 . Relative dielectric constant initially increases and then decreases. When the content of Sm 2 O 3 increases to 0.3 %, the varistor has ultrahigh dielectric constant, which is consistent with its narrowest grain-boundary barriers. The nonlinear coefficient increases from 2.51 to 4.13 with increase of Sm 2 O 3 from 0.0 to 0.4 %, and varistor of 98.8 %TiO 2 -0.5 %Nb 2 O 5 -0.3 %SiO 2 -0.4 %Sm 2 O 3 owns the highest grain-boundary barriers.

PREPARATION AND CHARACTERIZATION OF TiO₂-Ta₂O5-CaCO₃ VARISTOR CERAMICS BY HOT ISOSTATIC PRESSING (HIP) AND POST-ANNEALING

“…Because of nonlinear electrical behavior and sensitivity to instantaneous voltage fluctuations, varistor ceramics are widely used in circuits such as overvoltage protection, high voltage stability and high energy surge absorption [1][2][3]. The nonlinear behavior of a varistor is closely associated with the grain boundary barrier structure of polycrystalline ceramics [4].…”