Thermoelectric properties of the Heusler-type Fe2VTaxAl1−x alloys

• Published in: Journal of applied physics 2014-01, Vol.115 (3)
• Main Authors: Renard, Krystel, Mori, Arinori, Yamada, Yuichiro, Tanaka, Suguru, Miyazaki, Hidetoshi, Nishino, Yoichi
• Format: Article
• Language: English
• Subjects: Applied physics; Diffraction patterns; Ejection; Electrical resistivity; Figure of merit; Heavy elements; Maximum power; Power factor; Properties (attributes); Seebeck effect; Substitutes; Synchrotron radiation; Thermal conductivity; Thermoelectricity; X-ray diffraction
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4861419

This study focuses on the thermoelectric properties of the Heusler-type Fe2VTaxAl1−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 Fe2VAl 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 Fe2V1+yAl1−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 × 10−3 W/mK2 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 Fe2V1+yAl1−y alloys, i.e., 0.21–0.22 around 400–500 K for x = 0.05 and 500 K for x = 0.08.