Soft X-ray photoemission study of thermoelectric alloys Fe sub(2 - x - y)Ir sub(y)V sub(1 + x)Al and Fe sub(2 - x)V sub(1 + x - y)Ti sub(y)Al

• Published in: Journal of electron spectroscopy and related phenomena 2011-04, Vol.184 (3-6), p.236-239
• Main Authors: Soda, Kazuo, Harada, Shota, Kato, Masahiko, Yagi, Shinya, Inukai, Manabu, Miyazaki, Hidetoshi, Sandaiji, Yusuke, Tamada, Yuko, Tanaka, Suguru, Sugiura, Takahiro, Nishino, Yoichi
• Format: Article
• Language: eng ; fre ; ger
• Subjects: Alloys; Defects; Electronic structure; Iridium; Iron; Spectra; Thermoelectricity; Titanium
• ISSN: 0368-2048
• DOI: 10.1016/j.elspec.2011.03.001

The valence-band and core-level photoemission spectra of n-type thermoelectric Heusler(L2 sub(1))-type alloys Fe sub(2 - x - y)Ir sub(y)V sub(1 + x)Al and p-type ones Fe sub(2 - x)V sub(1 + x - y)Ti sub(y)Al have been studied to clarify the origin of the enhancement of their thermoelectric power. It is found that the excess V content x (V-rich for x 0 and Fe-rich for x 0) causes the drastic change in the valence-band electronic structure within the binding energy of [inline image]0.7 eV near the Fermi level E sub(F) and the evolution of the satellite structures in the V 2p core-level spectra with x increased. These spectral features are ascribed to the formation of the Fe or V anti-site defects in the off-stoichiometric alloys with non-zero x. The shift of the valence-band and core-levels towards the high (low) binding energy side is observed on partial substitution y of Ir (or Ti) for Fe (or V), which is attributed to the E sub(F) shift due to the common band formation with the Ir 5d or Ti 3d states incorporated into the main Fe-V 3d bands. The enhancement of the thermoelectric power in those Heusler-type alloys can be explained in terms of the observed changes in the valence-band electronic structure near E sub(F). Valence-band structure of Fe sub(2 - x - y)Ir sub(y)V sub(1 + x)Al and Fe sub(2 - x)V sub(1 + x - y)Ti sub(y)Al. Mid-pseudogap states derived from anti-site V and Fe defects. Band shift induced by partial substitution of Ir for Fe and V for Ti. Electronic structure change can explain enhancement of their thermoelectric power. Anti-site defects strongly affect thermoelectric properties in these alloys.