Production for high thermal stability NdFeB magnets

To improve sintered NdFeB magnets’ thermal stability and magnetic properties, combined addition of elements Cu and Gd was investigated. It was found that with Gd addition increase to 1.0%, the temperature coefficient α improved from −0.15 to −0.05%/°C (maximum working temperature 120 °C), but the remanence and the maximum energy product linearly decreased. With addition of Cu in Gd-containing magnets the intrinsic coercivity increased greatly, and the remanence increased also because of their density improvement, and optimum Cu content was achieved at 0.2%. Microstructure analysis showed that most of the Cu distributed at grain boundaries and led to clear and smooth morphologies. Magnets with high thermal stability α=−0.05%/°C and magnetic properties were obtained with addition of Gd=0.8% and Cu=0.2%.