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

This paper addresses the heating/cooling-induced formation, dissociation and phase separation during thermal oxidation of Sm<inf>2</inf>(Co, Fe, Cu, Zr)<inf>17</inf> alloys at 298.15 K-973 K, using real-time and room-temperature measurements. Whereas, Fe<inf>3</inf>O<inf>4</inf> forms at 673 K ≤ T ≤ 773 K, it transforms to CuFe<inf>2</inf>O<inf>4</inf> at 823 K ≤ T ≤ 973 K because of the incorporation of Cu⁺² into the octahedral Fe⁺² lattice sites in Fe<inf>3</inf>O<inf>4</inf>. CuFe<inf>2</inf>O<inf>4</inf> dissociates instantaneously upon cooling, and separates into layered structure of Cu-oxides at oxide-surface and Fe<inf>3</inf>O<inf>4</inf> underneath. A detailed discussion on possible reaction pathways leading to these phenomena during the heating/cooling cycle is presented here.