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Title: Pressure-induced phase transition and electrical properties of thermoelectric Al-doped Mg{sub 2}Si

A recent study has shown the thermoelectric performance of Al-doped Mg{sub 2}Si 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 Mg{sub 2}Si. 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.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)
  2. Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States)
  3. Canadian Light Source and Argonne National Laboratory, Argonne, Illinois 60439 (United States)
  4. Department of Applied Science, Faculty of Science, Okayama University of Science, Okayama (Japan)
  5. Canadian Light Source, Inc., Saskatoon, Saskatchewan S7N 2V3 (Canada)
Publication Date:
OSTI Identifier:
22492814
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 14; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DENSITY FUNCTIONAL METHOD; DOPED MATERIALS; ELECTRIC CONDUCTIVITY; ELECTRON DENSITY; FERMI LEVEL; MAGNESIUM SILICIDES; ORTHORHOMBIC LATTICES; PERFORMANCE; PHASE TRANSFORMATIONS; PRESSURE RANGE GIGA PA; REFLECTIVITY; TEMPERATURE RANGE 0273-0400 K; X-RAY DIFFRACTION