Synthesis and characterization of γ-Bi₂O₃ based solid electrolyte doped with Nb₂O₅

Abstract

γ-phase bismuth oxide is a well known high oxygen ion conductor and can be used as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). This study aims to determine new phases of Bi₂O₃-Nb₂O₅ binary system and the temperature dependence of the electrical transport properties. The reaction products obtained in open air atmosphere were characterized by X-ray powder diffractions (XRD). The unit cell parameters were defined from the indexes of the powder diffraction patterns. The γ-Bi₂O₃ crystal system were obtained by doping 0.01 < mole% Nb₂O₅ < 0.04 at 750 °C for 48 and 96 h. Thermal behaviour and thermal stability of the phases were investigated by thermal analysis techniques. Surface and grain properties of the related phases were determined by SEM analysis. The temperature dependence of the electrical properties of γ-Bi₂O₃ solid solution was measured by four-point probe d.c. conductivity method. In the investigated system, the highest value of conductivity was observed for σ _T = 0.016 ohm⁻¹ cm⁻¹ at 650 °C on 4 mole% Nb₂O₅ addition. The electrical conductivity curves of studied materials revealed regular increase with temperature in the form of the Arrhenius type conductivity behaviour.