Deformation mechanisms for high-temperature creep of high yttria content stabilized zirconia single crystals

Creep of 21 mol.% yttria-stabilized zirconia single crystals has been studied between 1,400 and 1,800 C. The creep parameters have been determined indicating a change of the controlling mechanism around 1,500 C. At higher temperatures recovery creep is found to be the rate controlling mechanism, with a stress exponent ≅ 3 and an activation energy ≅ 6 eV. Transition to glide controlled creep occurs below 1,500 C, associated with larger stress exponents (≅ 5) and activation energies (≅ 8.5 eV). TEM observations of the dislocation microstructure confirm this transition. The influence of the high yttria content, which is at the origin of the high creep resistance of these crystals, is discussed for each range of temperatures