Impedance analysis on electrical anisotropy of layer-structured Bi4V2(1−x)Co2xO11−δ single crystals

Single crystals of Bi4V2(1−x)Co2xO11−δ were prepared, and the complex impedance plots were analyzed in the directions parallel and perpendicular to the (Bi2O2)2+ layer assuming an equivalent circuit composed of resistances and constant phase elements. The change in conductivity of the perovskite block between phase transitions from the α-phase to the γ-phase was very large, and the conductivity of the perovskite block in the γ-phase was about 3 orders of magnitude larger than that of the (Bi2O2)2+ layer. The impedance plot simulated using each circuit parameter fitted well with the measured impedance plot. The electrical anisotropy of Bi4V2(1−x)Co2xO11−δ single crystals were indicated to result from the highly conductive perovskite block.