Dielectric relaxation in tetragonal tungsten bronze ceramics

Abstract

Ferroelectric tantalates with the tetragonal tungsten bronze (TTB) type structure were studied over a wide frequency range from 10 2 to 10 9 Hz. Complementary microwave measurements at 36 GHz and micro-Raman experiments were performed in order to extend the dielectric study. A high frequency relaxation was observed above 10 8 Hz and fitted to the Cole–Cole formula. Different qualitative models are proposed to explain the understanding of the origin of the high frequency relaxation in ferroelectrics. Among these, polar clusters of ferroelectric active off-centred Ta 5+ ions are considered.