Structural and dynamical studies of δ-Bi2O3 oxide-ion conductors . II. A structural comparison of (Bi2O3)1-x(M2O3)x for M = Y, Er, and Yb</SBT>
We report the results of diffuse elastic neutron scattering studies of the superionic solid solutions (Bi 2O 3) 1- x(Er 2O 3) x and (Bi 2O 3) 1- x(Yb 2O 3) x, and also the result of a Bragg diffraction study of (Bi 2O 3) 0.75(Er 2O 3) 0.25. All the data suggest that Er 3+-doped δ-Bi 2O 3 is structurally very similar to the fluorite-related solid solution (Bi 2O 3) 1- x(Y 2O 3) x studied previously, both in terms of the average structure as determined by Bragg scattering and in terms of local ordering on the anion sublattice as detected by diffuse scattering. The ordered regions are described as microdomains of a rhombohedral phase. The Yb 3+-doped materials also show short-range anion ordering, but over shorter distances than in the other two cases. There is evidence of cation ordering between Bi 3+ and Yb 3+ near the low-dopant boundary of the fluorite phase. The possible use of quasi elastic neutron scattering to monitor oxide-ion transport in the system (Bi 2O 3) 1- x(Er 2O 3) x is discussed.