On the oxygen stabilized Nd-rich phase in the Nd-Fe-B (-O) permanent magnet system

Lemarchand, D.; Vigier, Philippe; Labulle, B.

doi:10.1109/20.104826

Cited by 25 publications

(8 citation statements)

References 6 publications

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“…2(a) shows a series of selected area electron diffraction (SAD) patterns tilted from an Nd-rich phase. These strong and weak diffraction patterns have been suggested to arise from FCC-NdO and BCC-Nd 2 O 3 [5,6]. In contrast, TEM work by Chou et al [7] and by the present authors showed the dark field images were bright in the whole Ndrich phase, and therefore it ruled out of the possibility of two phases.…”

Section: Nd-rich Phasecontrasting

confidence: 52%

“…Fidler [3] observed an Nd-rich phase having a double hexagonal structure (so-called DHCPNd 2 O 3 ) in sintered magnets. After annealing at 1080 1C for 50 min, the DHCP phase would transform to an FCC NdO phase (NaCl prototype) [4] at O40.57 at% [5]. Under electron irradiation, the fundamental FCC patterns of NdO phase were superimposed by weak reflections.…”

Section: Introductionmentioning

confidence: 99%

“…Under electron irradiation, the fundamental FCC patterns of NdO phase were superimposed by weak reflections. Lemarchand et al [5] and Yin et al [6] attributed them to a BCC Nd 2 O 3 coexistence with an FCC NdO. However, TEM dark field did not favour two phases coexisting, and a BCC superlattice with twice the lattice parameter of the fundamental FCC lattice was suggested [7].…”

Section: Introductionmentioning

confidence: 99%

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In situ TEM study of Nd-rich phase in NdFeB magnet

Wang

2005

Journal of Magnetism and Magnetic Materials

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Hot stage in transmission electron microscope has been used to study the structure and stability of Nd-rich phase in NdFeB magnet. The present observation shows that the so-called complex cubic phase is in fact the prototype of Mn 2 O 3 (space group Ia 3) with lattice parameter of a ¼ 1:08 nm: The Nd-rich phase with P 3m1 structure (h-Nd 2 O 3 ) was first observed to be transformed from the BCC phase after in situ heating over 400 1C. The orientation relationship between these two structures satisfies as follows: (0 0 0 1) HCP //(2 0 0) BCC , ð10 1 0Þ HCP ==ð0 2 0Þ BCC ; ½ 1 2 1 0 HCP ==½0 0 1 BCC : It is argued that the h-Nd 2 O 3 was arising from the oxidation of the BCC Nd-rich phase rather than from Nd 2 Fe l4 B matrix phase as suggested in the literature. r

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Section: Nd-rich Phasecontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In situ TEM study of Nd-rich phase in NdFeB magnet

Wang

2005

Journal of Magnetism and Magnetic Materials

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“…[2][3][4][5][6][7][8][9][10][11][12][13] Most of the literature shows that oxide of fcc structure exists in a so-called Nd-rich phase in the grain boundaries. Nd-Fe-B sintered magnets are thought to have typical nucleation type coercivity mechanisms, as indicated by their initial magnetization curve.…”

Section: Introductionmentioning

confidence: 99%

Coercivity generation of surface Nd2Fe14B grains and mechanism of fcc-phase formation at the Nd/Nd2Fe14B interface in Nd-sputtered Nd–Fe–B sintered magnets

Fukagawa¹,

Hirosawa²

2008

Journal of Applied Physics

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The coercivity of surface grains of a Nd-Fe-B sintered magnet can be measured unequivocally if the magnet is a thin slab with the orientation of its c-axis parallel to the largest surface. Due to the loss of part of the neodymium-rich grain boundary phase, the surface Nd 2 Fe 14 B grains have low coercivity after machining. When a Nd layer is sputter deposited on the surface and annealed in the temperature range from 500 to 675°C, the surface coercivity recovers to its full value, which is identical to the coercivity of the bulk magnet from which the slab was cut. Transmission electron microscopy has indicated the formation of a fcc interfacial phase having a lattice constant a = 0.548 nm between the surface grains and the Nd layer in the specimen whose surface coercivity was recovered. In addition to a double hexagonal closed packed phase ͑metallic Nd͒, A-type Nd 2 O 3 has been observed in the inner region of the Nd film away from the interface. A-type Nd 2 O 3 having a hexagonal structure with a = 0.382 nm and c = 0.598 nm is the most stable phase of the neodymium oxides with 2:3 stoichiometry. Since the fcc phase is derived from metastable C-type Nd 2 O 3 having a cubic structure with a = 1.108 nm, the fcc phase is also a metastable phase. Therefore it is considered that the formation of the fcc phase results from the interfacial energy with the Nd 2 Fe 14 B grains.

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“…Previous studies have shown that the coercivity of Nd-Fe-B sintered magnets was structure sensitive and dependent on the distribution of Nd-rich phases [3], the distribution of misaligned grains [4], average grain size and size distribution [5]. It has been known that heat-treatment processes greatly affect the structure of the sintered magnet [6][7][8], in particular on the distribution of Nd-rich phases.…”

Section: Introductionmentioning

confidence: 99%