Lattice diffusion kinetics in Y2O3-stabilized cubic ZrO2single crystals: A dislocation loop annealing study

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Abstract
The shrinkage rates of small prismatic dislocation loops introduced by high-temperature plastic deformation in 9·4 and 18 mol% Y2O3-stabilized cubic ZrO2 single crystals have been determined via sequential observation of thin transmission electron microscopy foils annealed ex situ between 1100 and 1300°C. The shrinkage rates of individual loops were used to determine the diffusivity of the rate-controlling species, assumed to be Zr point defects (the Zr diffusivity is known to be less than the 0 diffusivity in this superionic conductor). Both vacancy and interstitial loops were present and exhibited approximately the same shrinkage rates. The Zr diffusivities in the 18 mol% Y2O3 alloy were approximately 15 times slower than those in the 9·4 mol% Y2O3 alloy. However, the activation energies for the two alloy concentrations, 5·3 ± 0·1 eV, were essentially identical. Traditional point-defect calculations suggest that cation transport involves a charged-vacancy cluster (V‥ O V″″Zx)″, with an apparent formation enthalpy of 2·8 eV and a migration enthalpy of 2·5 eV. The calculated charged vacancy cluster concentrations modestly decrease as the doping content increases. The lower cation diffusivities of the higher solute crystals are attributed to the higher density of yttrium-containing trapping and blocking centres, (Y′ZrV‥ O)′ and Y′Zr, respectively.

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