Detailed X-ray and neutron powder diffraction investigations were made of the defect structures of Co-doped solid electrolytes, Bi2V1-xCoxO5.5-3x/2 (where x was equal to 0.1 or 0.2), after quenching from high temperatures. It was found that the structure comprised alternating [Bi2O2]n2n+ and [V1-xCoxO3.5-3x/2]n2n- layers, with disorder being limited to the vanadate layer. The ideal V/Co coordination was octahedral, with corner-sharing of equatorial O ions. More exact results showed that the true structure was distorted, with disorder of both the apical and equatorial O ions, and with O vacancies concentrated in the equatorial positions. There were 2 main types of V/Co coordination: distorted octahedral and distorted tetrahedral. Most of the sites in both compositions were tetrahedral.

I.Abrahams, F.Krok, J.A.G.Nelstrop: Solid State Ionics, 1996, 90[1-4], 57-65