Patent Number: 7,824,506

Title: Nd-Fe-B magnet with modified grain boundary and process for producing the same

Abstract: In known methods, an improvement of the coercive force is realized by allowing the Dy metal or the like to present selectively in crystal grain boundary portions of a sintered magnet. However, since these are based on a physical film formation method, e.g., sputtering, through the use of a vacuum vessel, there is a mass productivity problem when a large number of magnets are treated. Furthermore, there is a magnet cost problem from the viewpoint that, for example, an expensive, high-purity Dy metal or the like must be used as a raw material for film formation. The method for modifying grain boundaries of a Nd--Fe--B base magnet includes the step of allowing an M metal component to diffuse and penetrate from a surface of a Nd--Fe--B base sintered magnet body having a Nd-rich crystal grain boundary phase surrounding principal Nd.sub.2Fe.sub.14B crystals to the grain boundary phase through a reduction treatment of a fluoride, an oxide, or a chloride of an M metal element (where M is Pr, Dy, Tb, or Ho).

Inventors: Machida; Kenichi (Osaka, JP), Suzuki; Shunji (Osaka, JP)

Assignee: Japan Science and Technology Agency

International Classification: H01F 1/057 (20060101)

Expiration Date: 2019-11-02 0:00:00