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Article Dans Une Revue RSC Advances Année : 2015

Origin of the highly anisotropic thermal expansion of the semiconducting ZnSb and relations with its thermoelectric applications

Résumé

This article is devoted to the thermal expansion of ZnSb combining experiments (neutron and X-ray) andcalculations based on density functional theory. Related properties are also studied such as: the zone-center(Raman and infrared) phonon modes, the dielectric (electronic and static) tensors, the phonondensity-of-states, the specific heats and the isotropic atomic displacement parameters. Our experimentaldata show highly anisotropic thermal expansion with large values along the a-direction. Concomitantly,a large increase of the Zn–Zn intra-ring distances and of one of the intra-ring Zn–Sb distances isobserved, while other interatomic distances do not significantly change. In agreement with ourcalculations, the thermal expansion has positive values along the three crystal directions except around30 K where it has weak negative values along the b and c-directions. This anomalous expansion is moreimportant along the c-direction and it is mainly due to phonon modes with frequencies up to 75 cm1.These modes are located in the S–Y–G (resp. G–Z) q-point range along the b (resp. c) direction. Phononmodes located in the G–X and in the Y–G–Z q-point range with frequencies up to 175 cm1 areresponsible for the positive large thermal expansion at room temperature along the a-direction. Themuch reduced anisotropy of the thermal conductivity is related to the lower Debye temperatures alongthe b and c-directions and mainly to the small transverse sound velocity between these directions.
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Dates et versions

hal-01217123 , version 1 (19-10-2015)

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P. Hermet, M. M. Koza, C. Ritter, C. Reibel, Romain Viennois. Origin of the highly anisotropic thermal expansion of the semiconducting ZnSb and relations with its thermoelectric applications. RSC Advances, 2015, 5, pp.87118. ⟨10.1039/c5ra16956a⟩. ⟨hal-01217123⟩
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