STRUCTURAL AND DYNAMIC STUDIES OF DELTA-BI2O3 OXIDE-ION CONDUCTORS .2. A STRUCTURAL COMPARISON OF (BI2O3)1-X(Y2O3)X, (BI2O3)1-X(ER2O3)X, (BI2O3)1-X(YB2O3)X

We report the results of diffuse elastic neutron scattering studies of the superionic solid solutions (Bi//2O//3)//1// minus //x(Er//2O//3)//x, and (Bi//2O//3)//1// minus //x(Yb//2O//3)//x, and also the result of a Bragg diffraction study of (Bi//2O//3)//0//. //7//5(Er//2O//3)//0//. //2//5. All the data suggest that Er**3** plus -doped delta -Bi//2O//3 is structurally very similar to the fluorite-related solid solution (Bi//2O//3)//1// minus //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.