Effect of Flux Addition on Mechanical and Microwave Dielectric Properties of Barium Zinc Tantalate Ceramics

Abstract

Radio frequency (RF) window sections used in high power microwave windows in the fusion system require high mechanical strength along with excellent microwave dielectric properties. Barium zinc tantalate, Ba(Zn1/3Ta2/3)O3 (BZT) exhibits high dielectric constant, small temperature coefficient of resonant frequency and high quality factor. Hence it is an important material for microwave window application in fusion reactor. In the present study, BZT ceramics was prepared by conventional solid state reaction. Calcination of the as milled raw powders at 1250°C for 6 h resulted in complete phase formation, which was then characterized by X-ray diffraction (XRD) for its primary crystal structure and composition. The synthesized BZT composition sintered at temperatures 1550° and 1600°C resulted in a maximum of 94% and 95% of the theoretical density respectively. A maximum of 97% of the theoretical density was achieved for the samples containing 0.5 wt% B2O3 when sintered at a temperature of 1500°C. The effect of B2O3 flux addition, prior to compaction processing, on the microstructure, microwave dielectric properties and mechanical properties of BZT ceramics is investigated. The dielectric properties were measured in the microwave range by Hakki-Coleman method and were correlated with the structural and mechanical properties. © 2014 The Indian Ceramic Society.