Influence of Nb Doping on Magnetic Properties of Nanocrystalline Nd-Fe-B Alloys

Abstract

The influence of Nb doping was studied on ribbons of nominal composition Nd Fe B Nb . The alloys were prepared by melt-spinning and then annealed at 973 K for 20 minutes. The magnetic characterization revealed that niobium addition improves substantially the magnetic properties of the studied alloys. The structural characterization showed that, in most alloys, the magnetically hard phase Nd Fe B precipitated as the main phase. This was not the case for the ternaries and for the Nd Fe B Nb alloys. Furthermore, the addition of Nb inhibited the precipitation of -Fe, independently of the Nd content. From the complete set of samples studied in this work, we found that the sample with nominal composition Nd Fe B Nb exhibited the highest coercive field kA/m while Nd Fe B Nb showed the highest maximum energy product, kJ/m .

XANES and XPS study of electronic structure of Ti-enriched Nd–Fe–B ribbons

“…One of the successful solutions to this task, in particular for nanostructured Nde FeeB alloys, is adding other chemical elements which help to control the grain growth during annealing. For these alloys (with low Nd content) the mechanism of their crystallization becomes modified when they are enriched with Ti, Nb and/or Mo, creating an optimized nanostructure that induces better magnetic properties of these materials [4,5]. In particular, it has been suggested that titanium addition retards the nucleation and growth of metallic iron, favoring crystallization of magnetically hard Nd 2 Fe 14 B phase [6].…”

Occupancy of 4d-states in T (T: Mo, Nb) from NEXAFS L 3,2 Spectra of Nd-Fe-B-T Alloys

“…From these remarks, it seems that more relevant variations in the 4d-state occupancy come from the alloys containing 2 at.% of the additive elements (both Mo and Nb) after the AQ samples have been subjected to thermal treatment. XRD analysis revealed a considerable amount (∼45%) of the metastable Nd 2 Fe 23 B 3 phase in both Mo 2 Nd 7 and Nb 2 Nd 7 TT samples [8]. The unit cell volume of this magnetic phase is slightly larger than the corresponding to Nd 2 Fe 14 B, but it has 224 atoms per cell instead of just 68 atoms (as in this latter phase), meaning that the free volume of the cell of the Nd 2 Fe 23 B 3 phase is smaller due to higher atomic density [10,11].…”

“…Urse et al explained the coercivity enhancement by the pinning of domain walls at grain boundaries where the additive precipitates, in the case of Modoped Nd-Fe-B thin fi lms [7]. For Nb-doped ribbons, it was found that a higher concentration of this additive is required than in the case of Mo in order to obtain higher coercivities and (BH) max [8]. Thus, a study of the electronic state of these elements becomes appropriate to elucidate the role they play as additives in Nd-Fe-B magnets.…”