Grain size effect on the electrical conductivity of submicron Sm-heavily-doped ceria

In order to investigate the grain size effect on the electrical conductivity of the submicron samarium-heavily-doped ceria , the Ce 0.8 Sm 0.2 O 1.9 (SDC20) ceramics with grain sizes from 128 nm to 533 nm were prepared by sintering at 1000–1300 °C in the air atmosphere. The crystalline structure, micro-morphology, density and electrical conductivity of the SDC20 ceramics were measured and characterized by XRD , SEM, TEM, Archimedes method and electrochemical impedance spectrum, respectively. All the sintered samples show the single SDC phase, low porosity and clean grain boundary without any impurities. The grain sizes of SDC ceramics grow continuously with the rising sintering temperature , and the relative densities increase as the sintering temperature rises from 1000 °C to 1200 °C and then decrease with the temperature from 1200 °C to 1300 °C. The specific grain boundary conductivity of SDC keeps decreasing while the grain and apparent grain boundary conductivities increase during the whole grain size range of 128–533 nm.