Structure and dielectric properties of solid solutions Bi7Ti4 + xWxTa1–2xO21 (x = 0–0.5)

Abstract

A number of solid solutions Bi₇Ti_{4 + x}W_xTa_1–2xO₂₁ (x = 0–0.5) have been synthesized from oxides by solid-phase reaction. The crystal structure, the electrophysical characteristics, and the microstructure of the prepared ceramic samples have been studied. According to X-ray powder diffraction, all the compounds are single-phase with the structure of mixed-layer Aurivillius phases (m = 2.5) with the orthorhombic crystal lattice (space group I2cm, Z = 2). Temperature dependences of the relative permittivity ε(T) of the compound have been measured, from which it has been found that the Curie temperature T_C of perovskite-like oxides Bi₇Ti_{4 + x}W_xTa_1–2xO₂₁ (x = 0–0.5) decreases linearly as substitution parameter x decreases. The activation energies of charge carriers have been found in different temperature ranges.