A Nd-Fe-O intergranular phase in Nd-Fe-B sintered magnets and its effect on coercivity

Journal Article · Mon May 01 04:00:00 EDT 1995 · IEEE Transactions on Magnetics

DOI:https://doi.org/10.1109/20.376242· OSTI ID:64574

Chen, Z; Wang, N; Song, X; Wang, X ^[1]

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1. Xi`an Jiaotong Univ. (China). Dept. of Materials Science and Engineering

The intergranular microstructure and coercivity of Nd richer Nd{sub x}Fe{sub 93{minus}x}B{sub 7} (x = 16--28) sintered magnets have been systematically studied by means of scanning electron microscopy, analytical transmission electron microscopy, scanning auger multiprobe, thermomagnetic analysis, magnetic measurement and annealing experiments. A new stable Nd-Fe-O ferromagnetic phase with a composition NdFe{sub 2}O{sub x} (x{approx}0.3) and a Curie temperature of 145 C is found in the intergranular regions of the magnets, due to the introduction of a considerable amount of oxygen during magnet processing and its segregation in the intergranular regions. The phase forms at {approximately}650 C and its volume fraction reaches a maximum of {approximately}4% in the Nd{sub 22}Fe{sub 71}B{sub 7} magnets. This new phase has a strong hindrance effect on the propagation of reversed domain walls between Nd{sub 2}Fe{sub 14}B grains, and thus leads to a considerable enhancement of coercivity. Raising the Curie temperature of this phase would be a new important approach to improve the high-temperature coercivity of Nd-Fe-B magnets.

• Sponsoring Organization: USDOE
• OSTI ID: 64574
• Journal Information: IEEE Transactions on Magnetics, Journal Name: IEEE Transactions on Magnetics Journal Issue: 3Pt2 Vol. 31; ISSN IEMGAQ; ISSN 0018-9464
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ALLOYS
COERCIVE FORCE
CURIE POINT
IRON ALLOYS
MAGNETIC PROPERTIES
MICROSTRUCTURE
NEODYMIUM ALLOYS
PERMANENT MAGNETS