Solid solution formation, densification and ionic conductivity of Gd- and Sm-doped ceria

The processes of solid solution formation, densification and electrical conductivity in samaria and gadolinia-doped ceria solid electrolytes were studied by Raman spectroscopy, density and impedance spectroscopy measurements. Bulk specimens of Ce0.9Gd0.1O1.95 and Ce0.8Sm0.2O1.9 were prepared by solid state reactions at several dwell temperatures and holding times. Hydrostatic density results show a fast increase in sintered density up to 1 h holding time. Raman spectra of specimens sintered for 1 h show a prominent band at 463 cm− 1 assigned to the cubic fluorite-type lattice of cerium oxide, and low-intensity bands at 344 and 363 cm− 1 attributed to free samarium and gadolinium sesquioxides, respectively. Solid solution completion was achieved only at temperatures above 1400 °C. Electrical conductivity measurements were used to study mass transport. Analysis of impedance data allowed for determining the activation energy for cation diffusion in Ce0.9Gd0.1O1.95 and Ce0.8Sm0.2O1.9 sintered specimens.