High-temperature creep resistance in rare-earth-doped, fine-grained Al2O3

High-temperature creep in undoped Al2O3 and La2O3- or Y2O3- Or Lu2O3-doped Al2O3 with a grain size of about 1 mu m is examined in uniaxial compression testing at temperatures between 1150 and 1350 degrees C. The high-temperature creep resistance in Al2O3 is highly improved by the rare-earth oxide doping in the level of 0.045 mol%, and the creep rate is suppressed in the order La2O3 < Y2O3 < Lu2O3. Rare-earth ions in each doped Al2O3 are found to segregate in Al2O3 grain boundaries without forming amorphous phase or second-phase particles. The activation energy for creep in undoped Al2O3 is estimated to be 410 kJ/mol, while it is about 800 kJ/mol in the three rare-earth oxide-doped Al2O3 The grain boundary diffusivity must be highly reduced by the segregation of the dopant cation in Al2O3 grain boundaries.