Crystal structure and dielectric properties of Ba_6−xCa_xTi₂Nb₈O₃₀ tungsten bronze ceramics

Abstract

Tungsten bronze oxide solid solution Ba_6−xCa_xTi₂Nb₈O₃₀ with space group P4bm (No. 100) was prepared by solid state reaction method. Rietveld refinements revealed a decrease in the volume of the unit cell and distortion of the Ti(Nb)O₆ octahedra with increasing Ca substitution. Ca substitution increased ferroelectric transition temperature T_C and coercive electric field E_C of the samples, decreased their dielectric losses D, and gradually declined the frequency dependence of the dielectric constants.