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Title: Thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1−x} alloys

This study focuses on the thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1−x} alloys (0≤x≤0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe{sub 2}VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe{sub 2}V{sub 1+y}Al{sub 1−y} compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5 × 10{sup −3} W/mK{sup 2} for x = 0.05 at 340 K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe{sub 2}V{sub 1+y}Al{sub 1−y} alloys, i.e., 0.21–0.22 around 400–500 K for x = 0.05 and 500 K for x = 0.08.
Authors:
; ; ; ;  [1] ;  [2]
  1. Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)
  2. Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)
Publication Date:
OSTI Identifier:
22275746
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM; CONCENTRATION RATIO; ELECTRIC CONDUCTIVITY; HEUSLER ALLOYS; INTERMETALLIC COMPOUNDS; IRON; STOICHIOMETRY; TANTALUM; TEMPERATURE DEPENDENCE; THERMAL CONDUCTIVITY; THERMOELECTRIC PROPERTIES; X-RAY DIFFRACTION