Structural and chemical stability of Sr-, Nb- and Zr-doped calcium manganite as oxygen-storage materials

Perovskites with multivalent transition-metal oxide show interesting properties in oxygen-storage capacity (OSC) due to the structural stability against a large amount of oxygen deficiency. In this study, two series of Mn-containing perovskites with oxygen nonstoichiometry δ, SrxCa1-xMn0.75Nb0.25O3−δ and SrxCa1-xMn0.5Nb0.25Zr0.25O3−δ, were synthesized and characterized before and after reduction in Ar-5% H2. The doping of Sr on Ca site improves the structural symmetry and stability against reduction and the additional doping of Zr on Mn site decreases the initiating temperature for oxygen loss, which could be related to the increase in lattice parameters. Two of the cubic perovskites, Sr0.75Ca0.25Mn0.75Nb0.25O3−δ and SrMn0.5Nb0.25Zr0.25O3−δ, were demonstrated to show excellent stability in the course of reduction-re-oxidation between Ar-5% H2 and oxygen. [Display omitted] •Two new series of calcium-manganite-based perovskites have been synthesized.•Sr doping causes the formation of cubic perovskite.•Cubic perovskites showed excellent reduction-re-oxidation properties.•Exsolution of nano-structured CaMnO2 on grain boundary was observed for the first time.