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(-2)Hz-1.5kHz; -150 to 1400 degrees 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 degrees 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 Zr-96 tracer diffusivity by secondary ion mass spectrometry at 1125-1460 degrees 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 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.