A stabilization mechanism of zirconia based on oxygen vacancies only

Abstract

The microscopic mechanism leading to stabilization of cubic and tetragonal forms of zirconia (ZrO 2 ) is analyzed by means of a self-consistent tight-binding model. Using this model, energies and structures of zirconia containing different vacancy concentrations are calculated, equivalent in concentration to the charge compensating vacancies associated with dissolved yttria (Y 2 O 3 ) in the tetragonal and cubic phase fields (3.2 and 14.4% mol respectively). The model is shown to predict the large relaxations around an oxygen vacancy, and the clustering of vacancies along the 111 directions, in good agreement with experiments and first principles calculations. The vacancies alone are shown to explain the stabilization of cubic zirconia, and the mechanism is analyzed.

Cluster-assembled cubic zirconia films with tunable and stable nanoscale morphology against thermal annealing

“…Thus, even if the data have been obtained following the same annealing protocol, it can be argued that the oxygen has a fundamental role in the phase change as well as in the aggregation of nanocrystals. 25,51,52 Evolution of grain size and film morphology with annealing temperature Fig. 7 shows the nanocrystal average crystallite size (diameter) of the cubic and monoclinic phases as a function of the annealing temperature.…”

First-principles thermodynamic modeling of atomic ordering in yttria-stabilized zirconia

“…39 Unlike 10YSZ, both equilibrated configurations of 8YSZ leave domains of material ͑up to 3-5 nm on a side͒ almost entirely devoid of Y and Vac. Both experiment 26 and theory 40 have previously led to suggestions that the vacancy distortions of the anion coordination sphere around Zr appearing as ZrO 8 → ZrO 7 , causing inefficient "packing," give rise to lattice expansion and thus the stabilization of the global cubiclike lattice symmetry. Thus, local atomic ordering, needing to accommodate the foreign ZrO 7 polyhedra, departs from the fluorite structure.…”

Ferroelastic switching of doped zirconia: Modeling and understanding from first principles

“…Accordingly, important goals in the development of advanced TBCs are phase stability at the higher temperatures (>1400 K) and improved toughness to mitigate a host of potential damage mechanisms [1]. For this purpose, it is essential to understand the fundamental origins of the mechanisms underlying the stabilization and toughening of the tetragonal phase.A common approach to stabilize the higher temperature forms of ZrO 2 involves doping with trivalent cations, most commonly Y 3+ , with the concomitant introduction of charged oxygen vacancies (F 2+ ) [5,6]. For TBCs, the useful composi-* carbogno@fhi-berlin.mpg.de…”

“…A common approach to stabilize the higher temperature forms of ZrO 2 involves doping with trivalent cations, most commonly Y 3+ , with the concomitant introduction of charged oxygen vacancies (F 2+ ) [5,6]. For TBCs, the useful composi-* carbogno@fhi-berlin.mpg.de…”