Impact of oxygen content on preferred localization of p- and n-type carriers in LaSrFeMnO.

The oxygen content in LaSrFeMnO, measured by coulometric titration in a wide range of oxygen partial pressure at various temperatures, was used for defect chemistry analysis. The obtained data were well approximated by a model assuming defect formation in LaSrFeMnO Fe and Mn oxidation reactions and charge disproportionation on Fe and Mn ions. The partial molar enthalpy and entropy of oxygen in LaSrFeMnO obtained by statistical thermodynamic calculations were found to be in satisfactory agreement with those obtained using the Gibbs-Helmholtz equations, thus further confirming the adequacy of the model. The impact of manganese substitution on defect equilibrium in LaSrFeMnO was shown to be attributed to a lower enthalpy of Mn oxidation reaction ( for the oxidation of Fe) and the charge disproportionation reaction on Mn ( for that on Fe). The former makes Mn ions more resistant to reduction than Fe. The latter favors the presence of Mn, Mn, and Mn ions in oxides in comparable concentrations. The distribution of charge carriers over iron and manganese ions was determined as a function of oxygen content in LaSrFeMnO.