The space charge density at the surface of yttria-stabilised zirconia (YSZ) containing 2–10 mol% yttria was determined from differential capacity measurements of YSZ/gold interfaces at 750–850 K. The oxygen vacancy concentration in the sub-surface layer was determined as a function of temperature and bias potential by fitting the experimental data at positive bias potentials to predictions based on a Boltzmann-type expression. The vacancy concentration at the interface increases with decreasing bias potential, and reaches a temperature-dependent maximum value at negative bias potentials. The thermal activation parameter for this process is 0.27–0.46 eV. A thermodynamic model for the near-surface defect structure of YSZ is proposed, in which oxygen vacancies are assumed to be distributed randomly over a fraction of the total number of oxygen sub-lattice sites. The fraction of sites that is available for oxygen vacancy distribution increases with yttria content and temperature.
ten Elshof, J. E., Hendriks, M. G. H. M., Bouwmeester, H. J. M., & Verweij, H. (2001). The near-surface defect structure of yttria-stabilised zirconia determined by measurement of the differential capacity. Journal of materials chemistry, 11(10), 2564-2571. https://doi.org/10.1039/b100923k