Microstructural and electrical investigation of flash-sintered Gd/Sm-doped ceria

Ceria-based ceramics can be considered among the most promising solid electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). In the present work, variously doped nanocrystalline ceria powders were flash-sintered, and the role of doping (Gd and Sm, 5–20 mol%) and sintering aid (Li and Co) on the final microstructure and the electrical behavior was investigated. Gdor Sm-doped nanocrystalline ceria powders were synthesized by co-precipitation method using ammonia solution as precipitating agent. The synthesized nanopowders were characterized by DSC-TG, XRD, and nitrogen physisorption analysis. The nanopowders were isostatically pressed and flash-sintered. The relative density was measured by hydrostatic balance, and the corresponding microstructure was observed by SEM. The electrical behavior was studied by EIS. Flash-sintered powder pellets showed different behaviors depending on the dopant and sintering aid. The electrical conductivity of the samples increased by increasing the relative density. Fully dense Gd-doped ceria samples, synthesized by co-precipitation, were obtained by flash sintering in very short times at 700 C. The total conductivity was comparable to that measured on samples sintered with conventional route at much higher temperatures such as 1500 C.