Campus Units

Chemistry, Materials Science and Engineering

Document Type

Article

Publication Version

Published Version

Publication Date

2006

Journal or Book Title

Inorganic Chemistry

Volume

45

Issue

26

First Page

10503

Last Page

10519

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

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