Determination of the Mn3+/Mn4+ ratio in La1−xSrxMnO3±d powders

The present work combines the results of two simple methods of determination of the Mn3+/Mn4+ ratio for La1−xSrxMnO3±d powders, prepared by citrate route, in which the Sr content, x, varies from 0.16 to 0.40. The ratio Mn3+/Mn4+ was successfully estimated combining the results of Temperature Programmed Reduction (TPR) analysis and redox titration. Moreover, the possible perovskite chemical formulas were established and a direct relationship between the Sr content and the Mn4+ amount was found. Morphological analyses such as grain size and surface area are also presented to better characterize the powders. Gas adsorption by Brunauer–Emmett–Teller method (BET) and scanning electron microscopy (SEM) were used to evaluate the agglomeration degree of powders and showed the inhibitory influence of Sr content on the growth of crystallites.

► TPR quantitative analyses were used to give the Mn3+/Mn4+ ratio in LSM samples.
► LSM stoichiometry was estimated combining TPR and ICP-MS results.
► For SOFC applications, the best Mn3+/Mn4+ ratio in LSM was found at Sr content of 16 mol%.