Thermoelectric properties of a Mn substituted synthetic tetrahedrite

Chetty, Raju and Kumar, Prem DS and Rogl, Gerda and Rogl, Peter and Bauer, Ernst and Michor, Herwig and Suwas, Satyam and Puchegger, Stephan and Giester, Gerald and Mallik, Ramesh Chandra (2015) Thermoelectric properties of a Mn substituted synthetic tetrahedrite. In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17 (3). pp. 1716-1727.

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Abstract

Tetrahedrite compounds Cu12-xMnxSb4S13 (0 <= x <= 1.8) were prepared by solid state synthesis. A detailed crystal structure analysis of Cu10.6Mn1.4Sb4S13 was performed by single crystal X-ray diffraction (XRD) at 100, 200 and 300 K confirming the noncentrosymmetric structure (space group I (4) over bar 3m) of a tetrahedrite. The large atomic displacement parameter of the Cu2 atoms was described by splitting the 12e site into a partially and randomly occupied 24g site (Cu22) in addition to the regular 12e site (Cu21), suggesting a mix of dynamic and static off-plane Cu2 atom disorder. Rietveld powder XRD pattern and electron probe microanalysis revealed that all the Mn substituted samples showed a single tetrahedrite phase. The electrical resistivity increased with increasing Mn due to substitution of Mn2+ at the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. Even though the thermal conductivity decreased as a function of increasing Mn, the thermoelectric figure of merit ZT decreased, because the decrease of the power factor is stronger than the decrease of the thermal conductivity. The maximum ZT = 0.76 at 623 K is obtained for Cu12Sb4S13. The coefficient of thermal expansion 13.5 +/- 0.1 x 10(-6) K-1 is obtained in the temperature range from 460 K to 670 K for Cu10.2Mn1.8Sb4S13. The Debye temperature, Theta(D) = 244 K for Cu10.2Mn1.8Sb4S13, was estimated from an evaluation of the elastic properties. The effective paramagnetic moment 7.45 mu(B)/f.u. for Cu10.2Mn1.8Sb4S13 is fairly consistent with a high spin 3d(5) ground state of Mn.

Item Type:	Journal Article
Publication:	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publisher:	ROYAL SOC CHEMISTRY
Additional Information:	Copyright for this article belongs to the ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	21 Jan 2015 05:33
Last Modified:	21 Jan 2015 05:33
URI:	http://eprints.iisc.ac.in/id/eprint/50714

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