Electrical conductivity, structure, and thermal expansion behaviour of ZrO 2-CeO 2-Gd 2O 3-Y 2O 3 solid solutions

Abstract

Mixed ionic and electronic conduction at low oxygen partial pressures make some compositions in the system ZrO 2-CeO 2-Gd 2O 3−y 2O 3 potential anode materials for solid oxide fuel cells. XRD showed the polycrystalline ceramics ( Zr 0.945 Y 0.055 O 1.973) 1− x ( Ce 0.85 Gd 0.15 O 1.925) x , x=0.186, 0.407, 0.673, and (Zr 0.87Y 0.13O 1.935) 1−y(Ce 0.85Gd 0.15O 1.925) 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.