Thermoelectric and electronic properties of chromium substituted tetrahedrite

Kumar, Prem DS and Tippireddy, Sahil and Ramakrishnan, Anbalagan and Chen, Kuei-Hsien and Malar, P and Mallik, Ramesh Chandra (2019) Thermoelectric and electronic properties of chromium substituted tetrahedrite. In: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 34 (3).

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Abstract

Cr substituted tetrahedrites with the chemical formula Cu12-xCrxSb4S13 (x = 0.15, 0.25, 0.35, 0.5, 0.75, 1.0) have been synthesised for thermoelectric study. Cr substitutes at the Cu site to optimize the thermoelectric properties and achieve a higher figure of merit (zT). X-Ray diffraction (XRD) analysis revealed that the tetrahedrite is the major phase with minor impurity phases. Electron probe microanalysis (EPMA) shows the formation of tetrahedrite main phase with near stoichiometry and the presence of Cu3SbS4, CuSbS2 and Sb as secondary phases. X-ray photoelectron spectroscopy (XPS) shows the oxidation state of Cu, Sb and S as +1, +3 and -2, respectively, whereas for Cr, it could not be identified. Temperature-dependent magnetic susceptibility of sample x = 0.75 shows antiferromagnetic correlation originating from the Cr ion. The calculated effective magnetic moment of 2.83 mu(B) per Cr atom indicates the presence of Cr+4 in this sample. The decrease in the electrical resistivity upon doping indicates the compensation of holes due to the substitution of Cr at the Cu site. But the x = 0.35 sample is not following the trend due to larger compensation of holes with an activation energy of 124.6 meV. The temperature-dependent behaviour of electrical resistivity shows the shift in the Fermi level from the valance band towards the band gap. The absolute Seebeck coefficient is positive throughout the temperature range and follows a similar trend as that of electrical resistivity, with the exception of the x = 0.35 sample. The electronic thermal conductivity reduces due to hole compensation caused by Cr substitution. Moreover, the substitution of Cr effectively reduces the lattice thermal conductivity due to point defect scattering of phonons. A maximum zT of 1.0 is achieved for sample x = 0.35 at 700 K.

Item Type:	Journal Article
Publication:	SEMICONDUCTOR SCIENCE AND TECHNOLOGY
Publisher:	IOP PUBLISHING LTD
Additional Information:	Copyright of this article belongs to IOP PUBLISHING LTD
Keywords:	tetrahedrite; XPS; DFT; magnetic properties; transport properties
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	01 Mar 2019 05:34
Last Modified:	01 Mar 2019 05:34
URI:	http://eprints.iisc.ac.in/id/eprint/61872

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