EXAFS studies of the cation sites in BIMEVOX fast-ion conductors

Extended X-ray absorption fine structure (EXAFS) has been used to study the local environment of the dopant ME cation in gamma-phase BIMEVOX.10, where ME = Co, Cu, Zn, Ni and Gd. It is known that Co, Cu and Zn occupy the V site and the EXAFS show that the local environment of these cations is relatively well-ordered with four nearest neighbour oxygen ions. In contrast, the EXAFS for the Gd cation shows a significantly higher coordination number and indicates that this cation predominantly occupies the Bi site. The EXAFS of the Ni samples provided no reliable structural information as they indicated that a significant fraction of the dopant was present as NiO, suggesting that there are difficulties in the preparation of phase-pure BINIVOX. (C) 1999 Elsevier Science B.V. All rights reserved.