Novel catalytic properties of quadruple perovskites.

Quadruple perovskite oxides 'O demonstrate a rich variety of structural and electronic properties. A large number of constituent elements for /'/-site cations can be introduced using the ultra-high-pressure synthesis method. Development of novel functional materials consisting of earth-abundant elements plays a crucial role in current materials science. In this paper, functional properties, especially oxygen reaction catalysis, for quadruple perovskite oxides CaCuFeO and MnO ( = Ca, La) composed of earth-abundant elements are reviewed.