Thermal stability of Sm-TM high temperature magnets at 300-550 degrees C

Investigation of thermal stability at 300-550 degreesC for the newly develo ped Sm(CowFevCuxZry)(z) high temperature magnets is reported in this paper, Three Factors are responsible for the irreversible losses at high temperat ures, One factor is the loss associated with a nonlinear induction demagnet ization curve, This results in significant loss when the magnet is exposed to temperatures higher than the maximum use temperature T-M. Another factor is the surface oxidation, which is more severe with increasing temperature and time at high temperature. Surface oxidation can be reduced by coating with a high temperature ceramic coating, The third factor is the result of metallurgical changes in the magnets. This loss is relatively small in the new magnets, which actually is < 2% after 360 hours at 550<degrees>C. The e xperiment confirms that coated magnets with T-M upw to 550 degreesC can be expected to have considerable life expectancy and relatively low losses at the intended T-M.