Relationship between Microstructure and Ionic Conductivity in Ytterbium Doped Ceria

Grain size dependence of ionic conductivities of Ce_1-xYb_xO_2-x/2 (x=0.10, 0.15, 0.20 and 0.25) was studied. The conductivity decreased with decreasing grain size and reached the minimum value at the grain size about 0.43-0.91 mum depending on different dopant concentration. Then the conductivity increased with a continuous decrease in grain size. TEM observation indicated that aforementioned conductivity behavior was partially associated with the microstructures. Microdomains were observed in grains using TEM. HRTEM micrographs and electron diffraction patterns showed that the formation the microdomains was restrained by the decrease in grain size. The microdomains could possibly lower the conductivity and the reduction of the microdomains possibly contributes to the increase in the conductivity when the grain size was smaller than 0.43-0.91 mum