Stability of tungsten-doped δ-Bi3YO6

Abstract The stability of bismuth yttrium oxide doped with tungsten, Bi3Y1−xWxO6+3x/2, on annealing in air for up to 1000 h at 650 °C was investigated using a.c. impedance spectroscopy and neutron diffraction. Compositions up to x = 0.2 all show some degree of conductivity decay, but only in the case of the x = 0.10 composition is this decay relatively small and not associated with a significant structural change. Details of the short range structure of this composition were investigated by reverse Monte Carlo modelling of total neutron scattering data and again reveal no significant changes prior to and post annealing. A preference for 〈100〉 oxide ion vacancy pair alignment is found in the structure, consistent with models for oxide ion conduction in these systems. Additionally, the total scattering analysis reveals a preferred vacancy association with the W6+ cations, which adopt a four coordinate geometry in this system.