Isotropic Zero Thermal Expansion and Local Vibrational Dynamics in (Sc,Fe)F3
Feiyu Qin1, Jun Chen1, Umut Aydemir2,3
1Department of Physical Chemistry, University of Science and Technology Beijing , Beijing 100083, China.
Inorganic Chemistry
|September 8, 2017
Summary
Scandium fluoride (ScF3) shows negative thermal expansion, but substituting some scandium with iron creates a zero thermal expansion material. This discovery offers new insights into controlling thermal expansion in advanced materials.
Area of Science:
- Materials Science
- Solid State Chemistry
- Crystallography
Background:
- Scandium fluoride (ScF3) exhibits significant negative thermal expansion (NTE).
- Controlling thermal expansion is crucial for advanced material applications.
- Tailoring NTE materials to achieve zero thermal expansion (ZTE) is an active research area.
Purpose of the Study:
- To investigate the suppression of NTE and induction of isotropic ZTE in ScF3 by partial substitution with iron.
- To elucidate the underlying mechanisms responsible for the observed thermal expansion behavior.
Main Methods:
- Synthesis of (Sc0.8Fe0.2)F3 (Fe20) solid solution.
- Synchrotron X-ray and neutron pair distribution function analysis.
- Extended X-ray absorption fine structure (EXAFS) spectroscopy.
Main Results:
- The Fe20 compound displayed isotropic zero thermal expansion (ZTE) with a coefficient of thermal expansion of -0.17 × 10^-6/K (300–700 K).
- Sc/Fe-F bonds were found to have positive thermal expansion (PTE).
- Local vibrational dynamics revealed decreased anisotropy in Sc/Fe-F bond vibrations.
Conclusions:
- A balance between PTE of chemical bonds and NTE from transverse vibrations leads to ZTE.
- This study expands the range of isotropic ZTE materials.
- Provides a detailed understanding of the ZTE mechanism in chemically modified NTE compounds.
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