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. Gd- or 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.