Re-analysis of defect equilibria and transport parameters in Y₂O₃-stabilized ZrO₂ using EPR and optical relaxation

The defect chemistry and transport properties of single-crystalline 9.5 mol% Y₂O₃-stabilized ZrO₂ selectively doped with 3d transition metal or rare earth ions, are analyzed. In-situ and ex-situ EPR (ESR) and optical absorption spectroscopy are applied to quantify the concentrations of the redox-active ions in specific valence states as a function of temperature and oxygen partial pressure, as well as to measure the chemical diffusion coefficients of oxygen. Relevant self-consistent defect equilibrium constants (oxygen incorporation, dopant ion ionization) and transport coefficients (mobilities of electrons, holes, and oxygen vacancies) are extracted. The analysis uses the significance of trapping effects for the thermodynamic factor of oxygen, and the fact that the activity coefficient of oxygen vacancies, even though non-trivial, does not depend on pO₂ or minor redox-active impurities.