Structure of Ba2In2 − xVxO5 + x phases: Complementarity of diffraction, Raman and absorption techniques

By combining X-ray and neutron diffraction with Raman and X-ray absorption spectroscopies, the location of vanadium in the structure of the Ba2In2 − xVxO5 + x solid solution and its local environment was evidenced. Vanadium is spread over the two indium sites of the Brownmillerite structure but its surrounding is tetrahedral. This involves the introduction of oxygen vacancies in the “octahedral” layers of Ba2In2O5 and the presence of indium with a six-fold coordination in the “tetrahedral” layers. The number of InO octahedra increases with the substitution rate which explains the stabilisation of cubic forms for substitution rate higher than 0.3.