Study on Fabrication of High Strength and High Ionic Conductive Cubic Zirconia Ceramics

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Y_2O_3-stabilized cubic zirconia ceramics is considered to be good candidate materials as an solid oxygen fuel cells (SOFC). However, the fracture strength and toughness of cubic zirconia are not enough high to apply to an electrolyte of planer-type SOFC.In the present study, fundamental research on fabrication of high strength and high ionic conductive cubic zirconia were investigated in ceramics/ceramics composites of tetragonal zirconia/cubic zirconia and alumina/cubic zirconia and Y_2O_3-Sc_2O_3 doped cubic zirconia systems In the system of tetragonal zirconia grains dispersed cubic zirconia composites of 5mol.%Y_2O_3 doped ZrO_2 fabricated at 1500。C in air for 12hr, the fracture strength and ionic conductivity (at 900。C) of composites were 525MPa and 0.05Scm^<-1>. The fracture strength and ionic conductivity (at 900。C) of 20vol.%Al_2O_3 grains dispersed cubic zirconia fabricated by post-HIPing were 355MPa and 0.06Scm^<-1>. On the other hands, fracture strength and ionic conductivity of 2mol%Y_2O_3-6mol%Sc_2O_3 doped cubic zirconia were 214MPa and 0.141Scm^<-1>. These present results indicated that high ionic conductive cubic zirconia with high fracture strength were excellent ceramics as an electrolyte of planer-type SOFC.