The appearance of an orthorhombic BIMEVOX phase in the system Bi2MgxV1 − xO5.5 − 3x/2 − δ at high values of x

The structural and electrical behaviour of an orthorhombic BIMEVOX phase Bi2Mg0.3V0.7O5.395 − δ is discussed. This composition lies close to the BIMEVOX solid solution limit in the pseudo-binary system Bi2MgO4–Bi2VO5.5 − δ. Unlike most other BIMEVOXes, the BIMGVOX system exhibits an orthorhombic polymorph above the composition limit for stabilisation of the tetragonal γ-phase. On heating, Bi2Mg0.3V0.7O5.395 − δ exhibits phase separation at around 650 °C, which is reversed at 840 °C. On cooling, the BIMEVOX phase is maintained throughout to room temperature. Small changes in structure and conductivity are evident between 500 and 700 °C and suggest a structural and or compositional change in the vandate layer of the BIMEVOX phase at these temperatures.