The Influence of Oxygen Activity on Phase Composition, Crystal Structure, and Electrical Conductivity of CaV_1–xMo_xO_3±δ

Abstract

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–δ 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–δ 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–δ series do not show phase separation. The nonmonotonic behavior of the conductivity and linear expansion of CaV1–xMoxO3±δ was shown when the oxygen activity in the N2-H2-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±δ individual phase remains unclear.

Keywords

• perovskite
• vanadate
• molybdate
• metal–like conductivity
• chemical expansion
• phase separation