Improvement of thermoelectric properties for half-Heusler TiNiSn by interstitial Ni defects

We have synthesized off-stoichiometric Ti-Ni-Sn half-Heusler thermoelectrics in order to investigate the relation between randomly distributed defects and thermoelectric properties. A small change in the composition of Ti-Ni-Sn causes a remarkable change in the thermal conductivity. An excess conten...

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Bibliographic Details
Published in:Journal of applied physics 2011-09, Vol.110 (6), p.063710-063710-6
Main Authors: Hazama, Hirofumi, Matsubara, Masato, Asahi, Ryoji, Takeuchi, Tsunehiro
Format: Article
Language:English
Subjects:
CRYSTALS
HEUSLER ALLOYS
INTERSTITIALS
MATERIALS SCIENCE
NICKEL ALLOYS
PHONONS
PHOTOEMISSION
POWER FACTOR
STOICHIOMETRY
TEMPERATURE RANGE 0273-0400 K
THERMAL CONDUCTIVITY
THERMOELECTRIC MATERIALS
THERMOELECTRIC PROPERTIES
THERMOELECTRICITY
TIN ALLOYS
TITANIUM ALLOYS
VACANCIES
X-RAY PHOTOELECTRON SPECTROSCOPY
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Summary:We have synthesized off-stoichiometric Ti-Ni-Sn half-Heusler thermoelectrics in order to investigate the relation between randomly distributed defects and thermoelectric properties. A small change in the composition of Ti-Ni-Sn causes a remarkable change in the thermal conductivity. An excess content of Ni realizes a low thermal conductivity of 2.93 W/mK at room temperature while keeping a high power factor. The low thermal conductivity originates in the defects generated by an excess content of Ni. To investigate the detailed defect structure, we have performed first-principles calculations and compared with x ray photoemission spectroscopy measurement. Based on these analyses, we conclude that the excess Ni atoms randomly occupy the vacant sites in the half-Heusler structure, which play as phonon scattering centers, resulting in significant improvement of the figure of merit without any substitutions of expensive heavy elements, such as Zr and Hf.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3633518