The defect chemistry of the perovskite phase was modeled by using the compound energy formalism and an associate model. In both cases, CALPHAD methodology was applied; meaning that all thermodynamic and phase diagram data of the phase were simultaneously and consistently reproduced. The differences between the two modeling methods were considered and the descriptions were submitted to a defect chemistry analysis. It was shown that the compound energy formalism was able to describe perfectly the defect chemistry of the perovskite phase whereas the associate model failed to reproduce it correctly. When using the associate model the choice of which associates to use was crucial in determining how well the system could be approximated. As the associates were not physically meaningful entities this choice had to be made arbitrarily. In the case of the compound energy formalism on the other hand a more physically realistic description of the system was achieved and fewer optimizing parameters were required. The reason for this was that the model description of the phase within the compound energy formalism was unambiguously constructed based upon measured physical properties of the phase. The advantage of the associate model was that the model description was simple compared to the rather cumbersome expression obtained for the compound energy formalism.

Calculation of Defect Chemistry Using the CALPHAD Approach. A.N.Grundy, E.Povoden, T.Ivas, L.J.Gauckler: Calphad, 2006, 30[1], 33-41