High temperature plastic deformation of 24–32 mol% yttria cubic stabilized zirconia (YCSZ) single crystals

The high temperature mechanical properties of yttria fully-stabilised cubic zirconia (YCSZ) single crystals with yttria content of 24, 28 and 32 mol% have been studied. Creep experiments have been carried out in air and argon atmosphere at temperatures between 1400 and 1700 °C, under nominal stresses from 67 to 280 MPa. The samples were oriented for easy glide, that is, with the compression axis on the <112> crystallographic direction, and lateral faces corresponding to {110} and {111} crystallographic planes. Using the phenomenological creep equation, the stress exponent, n, and activation energy, Q, have been estimated in two temperature ranges: 1400–1500 °C with n≈6.8 and Q≈9.2 eV, and 1500–1700 °C with n≈4.7 and Q≈5.9 eV. The strain rates obtained confirm that there is a very smooth increase in creep resistance with the yttria content for the studied range of composition. The dislocation substructure of the deformed samples has also been investigated via TEM. Conventional g·b analysis has been carried out and all the results have been compared to previous ones for lower yttria content YCSZ. On the basis of the creep parameters obtained and the microstructural observations, two deformation mechanisms are proposed, depending on the temperature used in the deformation experiments: glide controlled solute drag for the lower temperature range (T≈1400 °C) and climb controlled recovery creep for higher temperatures (T⩾1500 °C).