High-Temperature Internal Friction and Diffusion in Y_2O_3- and CaO-Stabilised ZrO_2

摘要

Internal friction measurements of polycrystalline tetragonal ZrO_2(2.8 mol% Y_2O_3) and of polycrystalline cubic ZrO_2 (7.8 mol% Y_2O_3) show a high temperature background with an activation enthalpy of ΔH_m = 6.5 and 5.3 eV, respectively. About the same activation enthalpies were found in tracer diffusion studies using ~(96)Zr on identical samples (ΔH_(Zr) = 6.3 and 5.1 eV). Therefore, the high temperature background attributed to cation diffusion controlled viscoelastic relaxation. In single crystal of ZrO_2-CaO (11-17 mol% CaO), an internal friction maximum at 1400 K (0.01 Hz) with ΔH_R = 4.0 eV was observed. It is attributed to the local reorientation of cation vacancy - Ca pairs. The activation enthalpies for cation diffusion (ΔH_(Ca) = 5.1 eV and ΔH_(Zr) = 5.3 eV) are higher than for the internal friction maximum indicating that local cation jumps are monitored.