Abstract
We report the crystal structure of Nd–Fe alloys as candidates for grain-boundary phases in Nd–Fe–B sintered magnets. We find that the crystal structure of the fluorite Nd–Fe alloys is stable for a wide composition range. We also demonstrate that solid solution of Ga is effective in stabilizing the fluorite crystal structure of Nd–Fe alloys, which is consistent with experimental observations reporting crystalline Nd–Fe alloys at the grain boundaries of Ga-added Nd–Fe–B permanent magnets.
Highlights
D–Fe–B sintered magnets are used in a wide range of industry products such as wind-turbine generators and the electric-vehicle motors, due to their high maximum energy products.1–8) it is problematic that the coercivity of Nd–Fe–B sintered magnets decreases significantly at high temperatures showing typically only
The key to improving the coercivity of Nd–Fe–B sintered magnets lies in the physical property of the main phase, Nd2Fe14B, and in microstructures, e.g. the chemical composition, the magnetism and the thickness of subphases.9–17) In particular, among the subphases in Nd–Fe–B sintered magnets, grain-boundary (GB) phases consisting mainly of Nd and Fe have impact on achieving the high coercivity. This is attributed to the fact that the electronic states of microstructure interfaces between the main phase and GB phases are responsible for the pinning effect to prevent the magnetization reversal caused by thermal fluctuation.18,19) Recent investigations have demonstrated that doping of metallic elements such as Al, Co, Cu, and Ga greatly modifies the microstructure including the GB
Phase improving the coercivity.20–23) In this sense, the atomic configurations and the magnetism of the GB phase is of significant importance
Summary
N d–Fe–B sintered magnets are used in a wide range of industry products such as wind-turbine generators and the electric-vehicle motors, due to their high maximum energy products.1–8) it is problematic that the coercivity of Nd–Fe–B sintered magnets decreases significantly at high temperatures showing typically only. Yuta Ainai1 , Yasutomi Tatetsu1,2, Asako Terasawa1, and Yoshihiro Gohda1* Nd–Fe alloys as fcc-type GB phases by first-principles calculations.
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