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Article
Superstructure in RE2-xFe4Si14-y (RE = Y, Gd−Lu) Characterized by Diffraction, Electron Microscopy, and Mössbauer Spectroscopy
Inorganic Chemistry
  • Mi-Kyung Han, Iowa State University
  • Ya-Qiao Wu, Iowa State University
  • Matthew Kramer, Iowa State University
  • Benjamin Vatovez, University of Missouri-Rolla, Rolla, Missouri
  • Fernande Grandjean, University of Missouri-Rolla, Rolla, Missouri
  • Gary J. Long, University of Liege
  • Gordon J. Miller, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
1-1-2006
DOI
10.1021/ic061117c
Abstract
Ternary rare-earth iron silicides RE2-xFe4Si14-y (RE = Y, Gd−Lu; x ≈ 0.8; y ≈ 4.1) crystallize in the hexagonal system with a ≈ 3.9 Å, c ≈ 15.3 Å, Pearson symbol hP20−4.9. Their structures involve rare-earth silicide planes with approximate compositions of “RE1.2Si1.9” alternating with β-FeSi2-derived slabs and are part of a growing class of rare-earth/transition-metal/main-group compounds based on rare-earth/main-group element planes interspersed with (distorted) fluorite-type transition-metal/main-group element layers. The rare-earth silicide planes in the crystallographic unit cells show partial occupancies of both the RE and Si sites because of interatomic distance constraints. Transmission electron microscopy reveals a 4a × 4b × c superstructure for these compounds, whereas further X-ray diffraction experiments suggest ordering within the ab planes but disordered stacking along the c direction. A 4a × 4b structural model for the rare-earth silicide plane is proposed, which provides good agreement with the electron microscopy results and creates two distinct Fe environments in a 15:1 ratio. Fe-57 Mössbauer spectra confirm these two different iron environments in the powder samples. Magnetic susceptibilities suggest weak (essentially no) magnetic coupling between rare-earth elements, and resistivity measurements indicate poor metallic behavior with a large residual resistivity at low temperatures, which is consistent with disorder. First-principles electronic-structure calculations on model structures identify a pseudogap in the densities of states for specific valence-electron counts that provides a basis for a useful electron-counting scheme for this class of rare-earth/transition-metal/main-group compounds.
Comments

Reprinted (adapted) with permission from Inorg. Chem., 2006, 45 (26), pp 10503–10519. Copyright 2006 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Mi-Kyung Han, Ya-Qiao Wu, Matthew Kramer, Benjamin Vatovez, et al.. "Superstructure in RE2-xFe4Si14-y (RE = Y, Gd−Lu) Characterized by Diffraction, Electron Microscopy, and Mössbauer Spectroscopy" Inorganic Chemistry Vol. 45 Iss. 26 (2006) p. 10503 - 10519
Available at: http://works.bepress.com/gordon-miller/93/