Novel catalytic properties of quadruple perovskites.

Quadruple perovskite oxides AA'3B4O12 demonstrate a rich variety of structural and electronic properties. A large number of constituent elements for A/A'/B-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 CaCu3Fe4O12 and AMn7O12 (A = Ca, La) composed of earth-abundant elements are reviewed.