Effect of Cr³⁺ substitution for V⁵⁺ in bismuth vanadate solid electrolyte

Solid electrolyte materials based on bismuth vanadate (Bi₄V₂O₁₁) exhibit 50–100 times more ionic conductivity than any other solid electrolyte materials which are in use in solid oxide fuel cell. Partially substituted trivalent Cr-doped Bi₄V_2-xMe_xO_11-5 (Me = Cr^III) has been prepared by solid state reaction technique. Three phases (α, β, γ) are observed in the unsubstituted compound. Alpha (α) is the low conducting room temperature phase and gamma (γ) is the high conducting phase observed at higher temperature. Stabilization of α, β and γ phases at room temperature depends on the Bi:V ratio and the nature of the dopant. These phases have been characterized by X-ray diffraction analysis. All the substituted phases (0≤x≤0.4) retain the low conducting α-phase. AC conductivity measurement of all the samples in the temperature range of 200°-700°C has been done. The change of slopes observed in the Arrhenius plots is in agreement with the phase transitions for all the studied compositions.