Hardening in Creep of Alumina by Zirconium Segregation at the Grain Boundary

Abstract

The effect of zirconium segregation on hardening in the creep of fine‐grained alumina was studied by using the tensile creep test. To avoid the effect of zirconia particle dispersion on creep, 100‐ppm‐zirconium‐doped alumina and 1000‐ppm‐zirconium‐doped alumina were fabricated by using a zirconium‐containing precursor. The scanning transmission electron microscopy/energy‐dispersive X‐ray spectroscopy study revealed that the zirconium was segregated at the alumina grain boundary. Doping even as little as 100 ppm of zirconium caused the hardening effect. The creep rate was further reduced by increasing the amount of zirconium dopant. Although the stress exponent of 2 was not affected by zirconium segregation, the apparent activation energy of the creep was found to be increased, from 520 kJ/mol for undoped alumina to 670 kJ/mol for 100‐ppm‐zirconium‐doped alumina and 760 kJ/mol for 1000‐ppm‐zirconium‐doped alumina. It was suggested that grain‐boundary sliding was accommodated by impurity‐drag‐controlled diffusional creep.