ELECTRICAL-CONDUCTIVITY, STRUCTURE, AND THERMAL-EXPANSION BEHAVIOR OF ZRO2-CEO2-GD2O3-Y2O3 SOLID-SOLUTIONS

Mixed ionic and electronic conduction at low oxygen partial pressures make some compositions in the system ZrO2-CeO2-Gd2O3-y2O3 potential anode materials for solid oxide fuel cells. XRD showed the polycrystalline ceramics (Zr0.945Y0.055O1.973)1-x(Ce0.85Gd0.15O1.925)x, x=0.186, 0.407, 0.673, and (Zr0.87Y0.13O1.935)1-y(Ce0.85Gd0.15O1.925)y, y=0.195, 0.42, 0.685, to be single phase solid solutions with the cubic fluorite structure. ac-impedance spectroscopy was applied to separate intra grain and grain boundary resistivities and to measure the electrical conductivity in air, argon, and wet hydrogen in the temperature range 250-1050°C. In most samples the grain boundary contribution to the total resistivity was small (∼10-15% at 300°C, decreasing with increasing temperature). In air a conductivity of 2×10-2S cm and seven times higher conductivity in wet hydrogen was observed for high Ce-contents at 1000°C. The linear thermal expansion coefficients are in the range 9-16×10-6 K-1, increasing with increasing temperature and Ce-content. © 1990.