XAFS characterization of La1−xSrxMnO3±δ catalysts prepared by Pechini's method

XAFS experiments at the Mn and Sr K-edges were carried out in order to investigate the short-range arrangement of Mn and Sr sites on La1−xSrxMnO3±δ highly doped perovskites (x = 0, 0.2, 0.4 and 0.6). The Mn K-edge EXAFS spectra show a static Jahn-Teller distortion of the MnO6 for x = 0 and 0.2, which is drastically reduced as x increases. The distortion of perovskite, characterized by the Mn-O-Mn tilt angle, progressively decreases with increasing Sr contents. Sr K-edge results indicated a decrease on the Sr-Mn coordination number upon Sr doping. Based on this and TPD results, a charge compensating mechanism is proposed suggesting a partial Mn oxidation and formation of Mn defect vacancies due to the introduction of Sr.