A Nd-Fe-O intergranular phase in Nd-Fe-B sintered magnets and its effect on coercivity
- 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, Vol. 31, Issue 3Pt2; Other Information: PBD: May 1995
- Country of Publication:
- United States
- Language:
- English
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