Structural and Electric Properties ofβ′-CuxV2O5

Single crystals of β ′ -Cu x V 2 O 5 have been successfully grown by a self flux method, and their structural, magnetic, and electric properties have been systematically investigated as a function of T and x . The properties of β ′ -Cu x V 2 O 5 are strikingly different from those of isostructural β- A x V 2 O 5 ( A = Na, Ag, etc.). With increasing x , the electrical conductivity of β ′ -Cu x V 2 O 5 along the b -axis increases monotonously and the metal-insulator transition occurs around x =0.60. The conductivity is highly anisotropic. For x < 0.43, the system undergoes a structural phase transition at ca. 200 K to an incommensurate (IC) phase. For x ≈0.40, the IC phase undergoes another phase transition to a commensurate one. A significant decrease in the conductivity has been found at the latter transition. The explanations of the metal-insulator transition and the structural phase transitions have been given in terms of randomness and Cu-ion ordering, respectively.