Barium titanate based dielectric sintered with a two-stage process

Abstract

A two-stage process was employed in this study to prepare dielectric material with high relative permittivity and low sintering temperature. In the first stage, the dielectric barium titanate (BaTiO 3) powders were uniformly coated with different amounts of glass via a high temperature melting process. The glass coated powders were then mixed with different amounts of LiF and sintered at temperatures from 850 to 950 °C using different dwell times in the second stage. The addition of LiF assisted the liquid phase formation of the glass, which lowered the sintering temperature and improved the densification of the material during the sintering process. Moreover, the pre-coated glass minimized the diffusion of LiF into the BaTiO 3 powders and thus dielectric properties of the sintered dielectrics were consistent with the samples without glass and LiF additions. Very dense sintered ceramics could be obtained using this two-stage process with a low sintering temperature, ≤900 °C. The relative permittivity achieved with 2 wt.% glass and 4 wt.% LiF additions sintered at 850 °C for 60 or 120 min was higher than 1700, which was only about 15% lower than pure BaTiO 3 sintered at 1450 °C for 4 h. The dielectric loss of the sintered dielectric was less than 0.01 being somewhat higher than with the pure BaTiO 3.