Formation of the face-centered cubic (FCC)-NdO x phase at Nd/Nd-Fe-B interface: A first-principles modeling

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Abstract

The development of advanced Nd-Fe-B permanent magnet materials with high coercivity draws much attention to the relation between coercivity and microstructure at the grain boundaries of the magnets. A disordered face-centered cubic (fcc)-NdO x phase formed at the interface of Nd/Nd-Fe-B is observed, and it is believed to take an important role in coercivity generation. To have a thorough understanding of the formation mechanism of this particular oxide and its relation to the surface coercivity, a ground state analysis for whole oxygen concentration in Nd-O has been performed by combining the LSDA + U and the cluster expansion method. Systematic calculations revealed that a sequent fcc-based structure formed by introducing oxygen vacancies into NdO is stable in almost all the 0-50% oxygen concentration range, whereas in a series of hexagonal close-packed (hcp)-based structures developed from hP5-Nd2O3 no stable structure is observed, which coincides with the experimental measurement very well. A further analysis of formation energies and relevant changes in electronic structures of single oxygen vacancy in various structures revealed the insight of such fcc-based phase formation and further explained the relation between the phase stability and coercivity.

Original languageEnglish
Pages (from-to)1133-1137
Number of pages5
JournalJOM
Volume66
Issue number7
DOIs
Publication statusPublished - 2014 Jul

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)

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