Mechanical spectroscopy of creep appearance in fine-grained yttria-stabilized zirconia

Mechanical spectroscopy or internal friction measurements were performed at high temperature in 3 mol% yttria-stabilized tetragonal zirconia. The mechanical loss spectrum is composed of a relaxation peak and a high temperature exponential background. It is shown that the transition from the peak to the exponential background accounts for creep appearance in the material. Mechanical loss is interpreted as due to grain boundary sliding. The associated activation enthalpy was found to be of 540 kJ/mol. In the low stress creep regime involved here a stress exponent of 2 and a grain size parameter of 1 are reported. A threshold stress behavior was observed, which can be associated with the obstacles limiting grain boundary sliding in this low stress regime.