Effect Of Grain Boundary Coating On The Conductivity Of CeO <2 Solid Electrolytes

CeO₂-based solid electrolytes have higher ionic conductivity in low-medium temperature compared with the traditional YSZ electrolyte. Try to improve the ionic conductivity of CeO₂-based electrolytes is of important theoretical and realistic significance.The 1 and 10 mol% Gd-doped ceria （1-and 10-GDC） solid solution powders were synthesized by coprecipitation method, then which were doped with 0.5 mol% Fe by the means of solid solution （SS） and preferred grainboundary segregation （GBS）, named as GDC-0.5Fe （SS） and （GBS）, respectively. All the synthesized powders only show the doped CeO₂ solid solution phase with grain sizes of 15.8-16.8nm. Then, the corresponding GDC ceramics before and after Fe-doping were sintered at 800℃ for 1 h. The sole doped CeO₂ solid solution phase appears in all the sintered samples with grain sizes of 59.8-112nm. The Fe doping through solid solution always leads to the decrement in the electrical conductivity of both 1-and 10-GDC samples, while that through controlled grain-boundary segregation results in the increment of 10-GDC sample. The ion transference numbers of 1-and 10-GDC-0.5Fe （GBS） samples are all above 0.95 in 300-650℃.The 10 mol%　Gd-doped ceria （10-GDC） solid solution powders were synthesized by coprecipitation method, then which were doped with 1 mol%　Co by the means of solid solution （SS） and preferred grainboundary segregation （GBS）, named as 10-GDC-1Co（SS） and （GBS）, respectively. All the synthesized powders only show the doped CeO₂ solid solution phase with grain sizes of 10.1-12nm. Then, the corresponding GDC ceramics before and after Co-doping were sintered at 1000 ℃ for 1 h. The sole ceria solid solution phase appears in all the sintered samples with grain sizes of 44.5-59.7nm. In the lower test temperature, the Co doping through controlled grain-boundary segregation leads to the increment in the electrical conductivity of 10-GDC samples, while with the temperature increasing, its electrical conductivity is very close to 10-GDC sample. The ion transference number of 10-GDC-1Co （GBS） sample is close to 0.8 in 650℃.