Synthesis and Study on Ionic Conductive (Bi_1-x,V_x)O_1.5-δ Materials with a Dual-Phase Microstructure

Homogeneous Bi₂O₃-V₂O₅ powder mixtures with different amounts of V₂O₅ content (≤15 mol%) were prepared by colloidal dispersion and sintering to high density. The sintered and annealed samples were studied by thermal analysis, quantitative X-ray diffraction and scanning electron microscopy. The electrical and ionic conductivities of the conductors were also measured by a four-probe direct current (DC) method. The results of the samples prepared at 600-800 °C and annealed for as long as 100 h show that the sintered samples consisting of a pure γ phase or δ + γ binary phase perform differently in conductivity. The highly conductive δ phase in the composition of Bi_0.92V_0.08O_1.5-δ enhances the electric conductivity 10-times better than that of the pure γ-sample (Bi_0.94V_0.06O_1.5-δ) between 400 and 600 °C. The compatible regions of the γ phase with the α- or δ phase are also reported and discussed, so a part of the previously published Bi₂O₃-V₂O₅ phase diagram below 800 °C is revised.