Structural and dynamical studies of δ-Bi₂O₃ oxide ion conductors. V. A study of the system (Bi₂O₃)_1-x(Eu₂O₃)_x by ¹⁵¹Eu Mössbauer spectroscopy

Cubic (x = 0.3) and rhombohedral (x = 0.2) phases have been prepared in the solid solution (Bi₂O₃)_1-x(Eu₂O₃)_x. The cubic material transformed to the rhombohedral form when subjected to a pressure of 4 GPa at a temperature of 873 K; at 4 GPa and 1073 K the transformation was to a phase of apparently monoclinic symmetry. ¹⁵¹Eu Mössbauer spectroscopy has been used to study all three forms of (Bi₂O₃)_0.7(Eu₂O₃)_0.3 in order to estimate the extent of anion-vacancy ordering in the solid solution. The Mössbauer linewidth from all samples is lower than that measured for CEu₂O₃, suggesting that the Eu atoms in these compounds have a single, well-defined, local environment.