Anomalous high temperature oxidation of Sm2(Fe,Co,Cu,Zr)17 particles

► Thermal oxidation of Sm2Co17 permanent magnet powders is not linear with temperature. ► Maximum weight gain occurs at 476 °C, and then decreases with increasing temperature. ► Thermogravimetric analysis combined with microchemical analysis (EDS) confirms Sm depletion at the surface. ► Competing sublimation and oxidation mechanisms occur in oxidizing atmosphere. ► Sm depletion does not occur in non-oxidizing conditions.