Two algorithms were proposed for the calculation of defect concentrations in A-site acceptor-doped ABO3 perovskites. The 2 models involved 9 species: including cation vacancies on the A- and B-sites. The small-polaron model was based upon 3 redox levels of the B-ion. A large-polaron model was based upon delocalized electrons, electron holes and all-trivalent B-ions. The sequential mathematical method permitted the calculation of the high-temperature O partial pressure-dependent properties of (La,Sr)MnO3 in a unified manner; regardless of the type of defect regime. Simulations were presented for O partial pressures ranging from 10-30 to 105atm. The 3 required equilibrium constants for (La,Sr)MnO3 had to be altered significantly from the published values in order to match the observed stoichiometry range. The main results were calculated by using the small-polaron model; involving only ionic species. The B-ion could be MnB' (Mn2+), MnBx (Mn3+) or MnB (Mn4+). The A/B ratio markedly affected the O stoichiometry, O-ion vacancy and cation vacancy concentrations, and the total conductivity. The defect model could simultaneously describe the observed stoichiometry and conductivity dependences upon O partial pressure.

Defect Chemistry Modelling of Oxygen-Stoichiometry, Vacancy Concentrations and Conductivity of (La,Sr)MnO3. F.W.Poulsen: Solid State Ionics, 2000, 129[1-4], 145-62