Pressure-induced phase transition and electrical properties of thermoelectric Al-doped Mg2Si

A recent study has shown the thermoelectric performance of Al-doped Mg2Si materials can be significantly enhanced at moderate pressure. To understand the cause of this phenomenon, we have performed in situ angle dispersive X-ray diffraction and infrared reflectivity measurements up to 17 GPa at room...

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Bibliographic Details
Published in:Journal of applied physics 2015-10, Vol.118 (14)
Main Authors: Zhao, Jianbao, Liu, Zhenxian, Gordon, Robert A., Takarabe, Kenichi, Reid, Joel, Tse, John S.
Format: Article
Language:English
Subjects:
Applied physics
Crystal lattices
Density functional theory
Density of states
Diffraction
Doping
Electrical conductivity
Electrical properties
Electrical properties and parameters
Electrical resistivity
Electron density
Fluorite
Gemstones
Helium
Intermetallic compounds
Magnesium compounds
MATERIALS SCIENCE
Metal silicides
Phase transitions
Power factor
Reflectance
Thermoelectric effects
Thermoelectricity
X-ray diffraction
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Summary:A recent study has shown the thermoelectric performance of Al-doped Mg2Si materials can be significantly enhanced at moderate pressure. To understand the cause of this phenomenon, we have performed in situ angle dispersive X-ray diffraction and infrared reflectivity measurements up to 17 GPa at room temperature. Contrary to previous experiment, using helium as a pressure transmission medium, no structural transformation was observed in pure Mg2Si. In contrast, a phase transition from cubic anti-fluorite (Fm-3m) to orthorhombic anti-cotunnite (Pnma) was observed in the Al-doped sample at 10 GPa. Infrared reflectivity measurements show the electrical conductivity increases with pressure and is further enhanced after the phase transition. The electron density of states at the Fermi level computed form density functional calculations predict a maximum thermoelectric power factor at 1.9 GPa, which is in good agreement with the experimental observation.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4933069