Study on La and Y co-doped ceria-based electrolyte materials

Co-doped ceria electrolytes of Ce0.8La0.2-xYxO1.9 (x=0.02, 0.06, 0.10, 0.14, 0.20) fine powders were prepared with the sol-gel method. The results of X-ray diffraction and Raman spectroscopy showed that all powders crystallite calcined at 800oC were single phase with cubic fluorite structure, the average crystallite sizes calculated by the Scherrer formula were between 27 and 34nm, which was in good agreement with the results of TEM and particle size distribution measurements. The thermal expansion curves of Ce0.8La0.2-xYxO1.9 were measured and the thermal expansion coefficients (TEC) between 100 and 800oC were calculated. For the samples of Ce0.8La0.2-xYxO1.9, in the temperature range of 700-850oC, when x=0.06, 0.10 and 0.14, much higher ionic conductivity was observed than those of the singly doped ceria with same dopant concentration (20% trivalent rare earth) and when x=0.06, maximal conductivity is obtained. It suggested that co-doping with appropriate ratio of lanthanum and yttrium can further improve the electrical performance of ceria-based electrolytes, and these co-doped samples may be the better electrolytes for intermediate-temperature solid oxide fuel cells