Order-disorder transformation in Fe-Pd alloy nanoparticles studied by in situ transmission electron microscopy

Kazuhisa Sato, András Kovács, Yoshihiko Hirotsu

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17 Citations (Scopus)


We have studied order-disorder transformation in Fe-Pd alloy nanoparticles by in situ transmission electron microscopy (TEM) and electron diffraction. The transformation is size-dependent, and the transformation temperatures are lower than those of the bulk alloys. The transformation proceeds continuously but rather steeply as the temperature increases, which differs from the first-order transformation observed in a bulk alloy or gradual transformation predicted by simulations for nanoparticles. Experimental results indicated that the continuous nature can be attributed to the distribution of the transformation temperature due to the distributions of both particle size and alloy composition. Quantitative intensity analyses of nanobeam electron diffraction (NBD) patterns indicated the existence of short-range order (SRO) inside disordered nanoparticles. The SRO as well as particle size distribution are responsible for the remaining weak superlattice reflections above the transformation temperature. In situ high-resolution TEM (HRTEM) observation revealed the existence of the SRO, which was consistent with the results obtained by NBD. We show that the disorder may not necessarily proceed continuously from the surface toward the center of the nanoparticle. Ordering from the disordered phase upon cooling was also observed by in situ HRTEM, which can be attributed to growth of the SRO.

Original languageEnglish
Pages (from-to)3305-3311
Number of pages7
JournalThin Solid Films
Issue number10
Publication statusPublished - 2011 Mar 1


  • Atomic order
  • Fe-Pd alloy
  • In situ electron microscopy
  • Nanoparticle
  • Order-disorder transformation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry


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