The Influence of Oxygen Activity on Phase Composition, Crystal Structure, and Electrical Conductivity of CaV1-xMoxO3±δ

Perovskite-like vanadate-molybdates are interesting from the point of view of their metal-like conductivity, which combines the correlated and free electron nature. A series of CaV1-xMoxO3-delta solid solutions was considered near the Mo concentration x = 0.4, where a difficult-to-perceive structural transition was previously detected. High-resolution transmission electron microscopy revealed the phase separation of CaV0.6Mo0.4O3-delta into nanoscale regions with different ratios of V and Mo concentrations, despite X-ray diffraction analysis exhibiting a homogeneous perovskite structure. The rest of the compositions from the CaV1-xMoxO3-delta series do not show phase separation. The nonmonotonic behavior of the conductivity and linear expansion of CaV1-xMoxO3 +/-delta was shown when the oxygen activity in the N-2-H-2-H2O gas mixture was varied, which is mainly determined by the partial decomposition of the perovskite phase. Against this background, the behavior of the electrical properties of the CaV1-xMoxO3 +/-delta individual phase remains unclear.

Automated summary

Perovskite-like vanadate-molybdates are interesting due to their metal-like conductivity and combination of correlated and free electron nature. This study focuses on a series of CaV1-xMoxO3-delta solid solutions, particularly near the Mo concentration x = 0.4, where a subtle structural transition was previously detected. The use of high-resolution transmission electron microscopy revealed phase separation in CaV0.6Mo0.4O3-delta, with nanoscale regions exhibiting different ratios of V and Mo concentrations, despite a homogeneous perovskite structure observed in X-ray diffraction analysis. Changes in oxygen activity also led to nonmonotonic behavior in the conductivity and linear expansion of CaV1-xMoxO3 +/-delta, which can be attributed to partial decomposition of the perovskite phase.