Mechanical loss, creep, diffusion and ionic conductivity of ZrO2-8 mol%Y2O3 polycrystals

Polycrystalline ZrO2-8 mol%Y2O3 was investigated by combining several experimental techniques on identical materials sintered out of the same high purity powder. The mechanical loss spectrum (damping and elastic modulus) was measured in a large frequency and temperature range (10−2Hz–1.5kHz; −150 to 1400°C). Damping due to point defect relaxation at low temperature and to viscoelastic relaxation at high temperature was revealed. The creep resistance was investigated with four-point bending tests (stress and temperature ranges: 20–75 MPa, 1100–1290°C), indicating Nabarro-Herring creep as the main rate-controlling mechanism. Both viscoelastic deformation and creep seem to be controlled by cation diffusion. Measurements of the 96Zr tracer diffusivity by secondary ion mass spectrometry at 1125–1460°C yielded an activation enthalpy of 460 kJ/mol. Close values were obtained for creep (440 kJ/mol) and viscoelastic relaxation (530 kJ/mol). Finally, the ionic DC-conductivity of these electrolytes was measured with high accuracy in the range 300–1250°C.