Crystal growth and electromagnetic properties of β-vanadium bronzes, β-A0.33V2O5 (A=Ca, Sr and Pb)

Single crystals of β-vanadium bronzes, β-A0.33V2O5 (A=Ca, Sr and Pb) were successfully grown by self-flux method (for A=Ca and Sr) and by a chemical transport reaction method using HCl gas as a transport agent (for A=Pb). By using crystals thus obtained, we measured electrical resistivity along the b-axis in the monoclinic structure. The distinct metal-insulator (M-I) transition was observed at 150 K for β-Ca0.33V2O5 and at 168 K for β-Sr0.33V2O5. The M-I transition is expected to be charge order type as observed in β-Na0.33V2O5. On the other hand, β-Pb0.33V2O5 shows no M-I transition but a smooth crossover from metal to insulator. This crossover seems to be due to the weak localization of very good one-dimensionality