Dielectric relaxation in layered oxides of the Aurivillius phase family

Abstract

Two new polycrystalline layered oxides Bi 2.33 Ca 0.17 Nb 1.33 W 0.17 O 7.5 and Bi 2.25 Ca 0.25 Nb 1.25 W 0.25 O 7.5 , in which the number of perovskite layers is equal to 1.5, have been synthesized. It has been revealed using X-ray powder diffraction analysis that both compounds have a single-phase composition and exhibit a structure of Aurivillius phases with orthorhombic unit cells corresponding to space group Cmm 2. The analysis of the temperature dependences of the permittivity in the frequency range from 1 kHz to 1 MHz has demonstrated that these compounds are characterized by relaxor properties. This manifests itself in the frequency dispersion of the ferroelectric-paraelectric transition temperature and high values of the diffusivity parameter: γ = 1.75 and 1.82.