Abstract
A statistical thermodynamic approach to analyze defect thermodynamics in strongly nonideal solid solutions was proposed and validated by a case study focused on the oxygen intercalation processes in mixed-conducting perovskite. The oxygen nonstoichiometry of Ni-doped lanthanum gallate, measured by coulometric titration and thermogravimetric analysis at in the oxygen partial pressure range , indicates the coexistence of , , and oxidation states. The formation of tetravalent nickel was also confirmed by the magnetic susceptibility data at , and by the analysis of -type electronic conductivity and Seebeck coefficient as function of the oxygen pressure at . The oxygen thermodynamics and the partial ionic and hole conductivities are strongly affected by the point-defect interactions, primarily the Coulombic repulsion between oxygen vacancies and/or electron holes and the vacancy association with cations. These factors can be analyzed by introducing the defect interaction energy in the concentration-dependent part of defect chemical potentials expressed by the discrete Fermi-Dirac distribution, and taking into account the probabilities of local configurations calculated via binomial distributions.
8 More- Received 25 April 2006
DOI:https://doi.org/10.1103/PhysRevB.74.064105
©2006 American Physical Society