Effect of A-site occupancy on phase transition and electric properties of CaxSr0.6-xBa0.4Nb2O6 ceramics

Abstract

Sr0.6Ba0.4Nb2O6 is an unfilled tetragonal tungsten bronze (TTB) with one empty A1/A2 site. In this work, Ca2+ doped Sr0.6Ba0.4Nb2O6, CaxSr0.6-xBa0.4Nb2O6 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) ceramics were designed to adjust A-site occupancy and then prepared by a conventional solid-state reaction method to study the influence of A-site occupancy on structure, phase transition, and electric properties of the ceramics. With increasing x, the ceramics vary from pure unfilled TTB to multiphase of the main TTB and a parasitic CaNb2O6. Nevertheless, the properties of CaxSr0.6-xBa0.4Nb2O6 are mainly decided by the TTB phase. Specifically, phase transition, dielectric permittivity, and polarization of the ceramics are closely related to the site occupancies of Sr2+ and Ba2+ at the A2 sites of the TTB phase.