TPR-study of Substitution Effects on Reducibility and Oxidative Non-stoichiometry of La0.8A'0.2MnO3+δ Perovskites

La0.8 A'0.2 MnO3+δ (A'=Sr, Ba, K, Cs) perovskites were studied by temperature-programmed reduction. The amount of non-stoichiometric oxygen was found to decrease from δ=0.16 for LaMnO3+δ to δ=0.07 (Sr-), 0.06 (Ba-), 0.07 (K-) and 0.03 (Cs-) substituted manganites. The reducibility at low and mean-temperatures (t<500°C) increased in the sequence La<(La, Sr)≈(La, Ba)<(La, Cs)<(La, K).