Issue 106, 2015

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

Abstract

This article is devoted to the thermal expansion of ZnSb combining experiments (neutron and X-ray) and calculations 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 phonon density-of-states, the specific heats and the isotropic atomic displacement parameters. Our experimental data 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 is observed, while other interatomic distances do not significantly change. In agreement with our calculations, the thermal expansion has positive values along the three crystal directions except around 30 K where it has weak negative values along the b and c-directions. This anomalous expansion is more important along the c-direction and it is mainly due to phonon modes with frequencies up to 75 cm−1. These modes are located in the SYΓ (resp. ΓZ) q-point range along the b (resp. c) direction. Phonon modes located in the ΓX and in the YΓZ q-point range with frequencies up to 175 cm−1 are responsible for the positive large thermal expansion at room temperature along the a-direction. The much reduced anisotropy of the thermal conductivity is related to the lower Debye temperatures along the b and c-directions and mainly to the small transverse sound velocity between these directions.

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

Supplementary files

Article information

Article type
Paper
Submitted
21 Aug 2015
Accepted
06 Oct 2015
First published
06 Oct 2015

RSC Adv., 2015,5, 87118-87131

Author version available

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

P. Hermet, M. M. Koza, C. Ritter, C. Reibel and R. Viennois, RSC Adv., 2015, 5, 87118 DOI: 10.1039/C5RA16956A

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