Study of electrical conductivity and phase transition in Bi2O3-V2O5 system

The solid solutions of bismuth-vanadate were prepared by the conventional solid-state reaction. The sample characterization and the study of phase transition were done by using FT-IR, X-ray diffraction (XRD) and DSC measurements. AC impedance measurements proved that the oxide ion conductivity predominantly arises from the grain and grain boundary contributions as two well-defined semicircles are clearly seen along with an inclined spike. The electrical conductivity of Bi2O3-V2O5 has been studied at different temperatures for various molar ratios. The isothermal conductivity increases with an increase in the concentration of V2O5 due to the vacancy migration phenomenon. It has been found that the conductivity of different compositions of Bi2O3-V2O5 increases and shows a jump in the temperature range 230-260 degrees C due to the phase transition of BiVO4 from monoclinic scheelite type to that of tetragonal scheelite type. The endothermic peak in DSC at around 260 degrees C reveals the phase transition, which is also confirmed by the XRD and FT-IR analysis. The XRD patterns confirmed the monoclinic structure of BiVO4.