Studies on structural, morphological, and electrical properties of Ga3+ and Cu2+ co-doped ceria ceramics as solid electrolyte for IT-SOFCs

Abstract

The present study highlights the effect of Ga3+ and Cu2+ co-doping on the crystal structure, surface morphology and ionic conductivity of ceria ceramics in the system Ce0.8Ga0.2-xCuxO2-δ for potential applications as the solid electrolyte material in the intermediate temperature solid oxide fuel cells (IT-SOFCs). Ultrafine Ce0.8Ga0.2-xCuxO2-δ (for x = 0, 0.05, 0.1, 0.15, and 0.2) nanopowders were prepared via glycine nitrate auto-combustion method. Phase identification, microstructural, and ionic conductivity of all the ceria ceramics were observed by powder XRD, SEM, TEM, and impedance analyses, respectively. Rietveld structural analysis using powder XRD pattern for all the co-doped systems confirms cubic fluorite type structure having Fm-3m space group, similar to cerium oxide. All these samples were found to have density above 85% after sintering at 1300 °C for 4 h. Raman spectra revealed the oxygen vacancies in all the compositions. Thermal analysis for change in weight and thermal expansion coefficient with temperature were performed by TGA and high temperature XRD measurements, respectively. Thermal expansion coefficient of the developed electrolytes matches with the commonly used electrode materials. The composition Ce0.8Ga0.05Cu0·15O1.825 was found to demonstrate the maximum ionic conductivity with the least activation energy among all the existing co-doped ceria ceramics. These features make it a promising candidate in the IT-SOFC as the electrolyte material.