Grain boundary grooving in polycrystalline oxides and surface diffusion coefficient in polycrystalline alumina

Grain-boundary grooving was studied on polished surfaces of polycrystalline oxides as yttria stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ) and alumina (Al2O3). The equilibrium groove angles (psi), measured by optical interferometry, showed no significant influence of the annealing temperature and atmosphere. The grain-boundary energy to surface energy ratios vary in the narrow range 0.487 to 0.534 for YSZ, 0.452 to 0.534 for CSZ and 0.695 to 0.725 for Al2O3 In the case of Al2O3 it was determined that surface diffusion is the dominant mechanism for mass transport. In the temperature range 1273-1763K the transport process depends mainly on the structural damage in the near surface region caused by mechanical polishing. The surface diffusion coefficient was calculated as D-s(cm(2)/s)=0.48exp[-256(kJ/mol)/RT].