Temperature dependence of Bi2O3 structural parameters close to the α–δ phase transition

Abstract

This article presents the results of in situ X-ray powder diffraction, Raman spectroscopy, and electrical impedance spectroscopy of the α-phase of Bi2O3, at 0.1 MPa in the temperature range below and above the α–δ-phase transition. This work demonstrated subtle nonlinear temperature variations of the cell parameters, of the hard-mode Raman shift, and of the activation energy of electrical conductivity in the temperature range about 100–120°C below the α–δ phase transition temperature T Tr ≈ 725°C in Bi2O3. At T < 600°C, the linear variation of the inverse dielectric susceptibility (χ −1) correlates well with the hard mode frequency shift Δ(ω 2) of Raman A1g mode as Δ(χ −1)/Δ(ω 2) ≈ 5.5 × 10−7 cm2. A structural model describing the mechanism of O2− anion distribution and electric dipole disordering in the vicinity of T Tr is discussed.