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Formation de phase et effets magnétocaloriques de LaFe(11.5)Si(1.5)B(x).

Phase formation and magnetocaloric effects in LaFe(11.5)Si(1.5)B(x).

Auteurs : ZHANG H., LONG Y., GSCHNEIDNER K. A. Jr, et al.

Résumé

The phase formation, structure, and magnetocaloric effect in as-cast and annealed LaFe(11.5)Si(1.5)B(x) (x= 0, 0.2, 0.5 and 1.0) compounds have been studied. Rietveld analyses of the x-ray powder diffraction patterns indicate that the cubic NaZn(13)-type La(Fe, Si)13 (1:13) phase is the main phase in the as-cast LaFe(11.5)Si(1.5)B(0.5) and LaFe(11.5)Si(1.5)B(1.0) alloys. Unlike in ternary silicides, heat treatment at 1373 K for 2 weeks does not facilitate the formation of the 1:13 phases in the quaternary boron compounds. Wavelength dispersive spectrometry analysis shows that the boron atoms do not occupy the interstitial positions as carbon and hydrogen do in the La(Fe, Si)13 compounds, but form Fe(2)B. The Curie temperatures of LaFe(11.5)Si(1.5)B(x) alloys increases in a nearly linear fashion from 183 to 196 K from x= 0 to x= 1.0. The maximum magnetic entropy changes, for a magnetic field change of 0-50 kOe decrease from 21.3 to 14.5 J/kg.K with increasing B content. The first order field induced itinerant electron metamagnetic transition, which accounts for the large entropy changes value, changes to second order when the B content reaches x= 1.0.

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Pages : 2009-3

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Détails

  • Titre original : Phase formation and magnetocaloric effects in LaFe(11.5)Si(1.5)B(x).
  • Identifiant de la fiche : 2009-1609
  • Langues : Anglais
  • Source : 3rd International Conference on Magnetic Refrigeration at Room Temperature
  • Date d'édition : 11/05/2009

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