Superstructure in RE2-xFe4Si14-y (RE = Y, Gd−Lu) Characterized by Diffraction, Electron Microscopy, and Mössbauer Spectroscopy

Supplemental Files
Date
2006-01-01
Authors
Han, Mi-Kyung
Wu, Ya-Qiao
Kramer, Matthew
Miller, Gordon
Vatovez, Benjamin
Grandjean, Fernande
Long, Gary
Miller, Gordon
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Research Projects
Organizational Units
Chemistry
Organizational Unit
Journal Issue
Series
Department
Materials Science and EngineeringChemistry
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.

Description
Keywords
Citation
DOI
Collections