The shrinkage rates of small prismatic dislocation loops, which had been introduced by the high-temperature plastic deformation of 9.4 and 18mol%Y2O3-stabilized cubic zirconia monocrystals, were determined by means of the sequential observation of thin transmission electron microscopic foils which were annealed at temperatures of between 1100 and 1300C. The shrinkage rates of individual loops were used to determine the diffusivity of the rate-controlling species. These were assumed to be Zr point defects (since the diffusivity of Zr was known to be less than that of O in this super-ionic conductor). Both vacancy and interstitial loops were present, and exhibited approximately the same shrinkage rates. The Zr diffusivities in the 18mol%Y2O3 material were some 15 times lower than those in the 9.4mol%Y2O3 material. However, the activation energies for the 2 alloy concentrations were essentially identical (5.3eV). Traditional point defect calculations suggested that cation transport involved a charged vacancy cluster, (Vo••VZr””)”, with an apparent formation enthalpy of 2.8eV and a migration enthalpy of 2.5eV. The calculated charged vacancy cluster concentrations decreased slightly as the dopant content was increased. Lower cation diffusivities in crystals with higher solute contents were attributed to the higher density of Y-containing trapping and blocking centers, (YZr’Vo••)• and YZr’, respectively.

Lattice Diffusion Kinetics in Y2O3-Stabilized Cubic ZrO2 Single Crystals: a Dislocation Loop Annealing Study. F.R.Chien, A.H.Heuer: Philosophical Magazine A, 1996, 73[3], 681-97