Development of new catalysts using an unique crystal structure in metastable iron-based mixed oxides

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Rare-earth-iron mixed oxides with hexagonal structure (h-REFeO3) are metastable and the synthesis of h-REFeO3 is usually difficult. In this work, the crystallization process of the precursors obtained by co-precipitation and Pechini methods was investigated in detail to synthesize h-REFeO3. It was found that the crystallization from amorphous to hexagonal phase and the phase transition from hexagonal to orthorhombic phase occurred at a similar temperature range. Single-phase h-REFeO3 was obtained by adjusting heating time during calcination process.To develop highly active catalysts for C3H8 combustion, we investigated the solvothermal synthesis of tradition metal-modified h-YbFeO3. The activity of Mn-modified h-YbFeO3 samples showed much higher activity than those of h-YbFeO3 modified by other transition metal cations such as Ni, Co or Cu ions. The catalyst was found to show excellent activity for the combustion of C3H8 that exceeds the activity of Pd/Al2O3.