Influence of Bi2O3 additive on the electrical conductivity of calcia stabilized zirconia solid electrolyte

Abstract

A few compositions of Bi2O3-doped calcia stabilized zirconia (Zr0.88−xBixCa0.12O2−δ; x=0.0, 0.02, 0.05, 0.10) were prepared via solid state reaction route. Addition of Bi2O3 decreased the sintering temperature of calcia stabilized zirconia (CSZ) and also augmented the growth of zirconia grains. Dense ceramic systems were formed in a temperature range of 1200–1300°C. X-ray Rietveld refinement analysis of the system revealed the formation of cubic zirconia phase at room temperature. Microstructural studies of the sintered pellet depicted highly dense grain morphology. XPS spectra of the compositions confirmed the elemental confinements and various characteristic valence states of the constituents. Thermal expansion coefficient of the Bi2O3 doped CSZ system was found to be compatible with the other components of solid oxide fuel cells (SOFC). Furthermore, conductivity analysis evidenced an Arrhenius type thermally activated ionic conduction above 300°C. The electrical conductivity of the system was found to increase with bismuth content up to x=0.05, thereafter decreased due to less solubility of Bi3+ into zirconia matrix. A high conductivity ∼0.019Scm−1 was achieved for 5mol% Bi2O3 calcia-codoped cubic zirconia system at 760°C. Thus, cost effective bismuth codoped calcia stabilized zirconia might be a possible alternative to yttria stabilized zirconia (YSZ), due to its ionic conductivity comparable to that of the YSZ.