Heating/cooling-induced formation, dissociation and phase separation of CuFe2O4 during thermal oxidation of Sm2(Co, Fe, Cu, Zr)17 permanent magnet

Abstract

This paper addresses the heating/cooling-induced formation, dissociation and phase separation during thermal oxidation of Sm2(Co, Fe, Cu, Zr)17 alloys at 298.15 K-973 K, using real-time and room-temperature measurements. Whereas, Fe3O4 forms at 673 K ≤T≤ 773 K, it transforms to CuFe2O4 at 823 K ≤T≤ 973 K because of the incorporation of Cu+2 into the octahedral Fe+2 lattice sites in Fe3O4. CuFe2O4 dissociates instantaneously upon cooling, and separates into layered structure of Cu-oxides at oxide-surface and Fe3O4 underneath. A detailed discussion on possible reaction pathways leading to these phenomena during the heating/cooling cycle is presented here.