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

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 TTr ≈ 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(ω2) of Raman A1g mode as Δ(χ-1)/Δ(ω2) ≈ 5.5 × 10-7 cm2. A structural model describing the mechanism of O2- anion distribution and electric dipole disordering in the vicinity of TTr is discussed. [ABSTRACT FROM AUTHOR]