The Influence of Sintering Temperature on Phase Composition and AC Breakdown Field Strength of SrTiO3-PbTiO3-Bi2O3-nTiO2 High-voltage Ceramics

摘要

SrTiO3-PbTiO3-Bi2O3-nTiO2 (SPBT) dielectric material has the characteristics of high withstand voltage, high dielectric constant, low loss, etc., so it is widely used in the manufacture of voltage equalizing capacitors for high-voltage circuit breakers and lightning arresters. With the development of UHV power transmission, in order to ensure the safe and stable operation of power equipment, higher requirements are put forward for the voltage resistance of capacitors. The ceramic material completes the densification of the porcelain body through the sintering process to form the material's dielectric properties, which is an important factor affecting the electric strength of ceramic capacitors. In this paper, the influence of sintering temperature on phase composition and AC breakdown field strength of SPBT high-voltage ceramics is studied. The results show that as the sintering temperature increases, the porosity of the ceramic decreases and the density of the ceramic body increases. The volatilization of PbO and Bi2O3 increases with the increase of sintering temperature, forming titanium-rich flaky second phase crystals above 1245°C. As the sintering temperature continues to increase, the surface of SPBT high-voltage ceramic capacitors appears as a piece of needle-like and massive crystal. The shaped second phase crystal provides a channel for crack propagation under the action of an external AC electric field, which greatly reduces the breakdown field strength of the ceramic capacitor.