Influence of reduction annealing on the characteristics of O₂ - YSZ based oxide ceramics

As a possible candidate of the electrolyte of solid oxide fuel cells (SOFC), ceria substituted YSZ (yttria stabilized zirconia) ceramics have been fabricated. We have already reported that ceria ceramics have improved in strength based on their chemical expansion on reduction annealing. Therefore, we examined the changes in flexural strength and ionic conductivity on reduction annealing. Before annealing both properties decreased with the substitution amount of ceria. However, the reduction annealing treatment improved the strength of the sample, of which degree was proportional to the amount of ceria substituted. Moreover, the 1 mol% ceria-substituted sample had high ionic conductivity and high flexural strength. The sample with that composition sintered under reduction atmosphere improved its mechanical strength by 13% on annealing in air.