Enhanced thermoelectric performance of nanostructured manganese telluride via antimony doping P.R. Sreeram a , V. Ganesan b , Senoy Thomas a, c , M.R. Anantharaman a, c, * a Department of Physics, Cochin University of Science and Technology, Cochin, 682022, Kerala, India b UGC-DAE Consortium for Scientific Research, Indore, 452001, India c Inter University Centre for Nanomaterials and Devices, Cochin University of Science and Technology, Cochin, 682022, Kerala, India article info Article history: Received 4 January 2020 Received in revised form 6 April 2020 Accepted 25 April 2020 Available online 1 May 2020 Keywords: MnTe Thermoelectric properties Sb doping Seebeck coefficient Power factor abstract Manganese telluride is a good thermoelectric material for medium temperature applications. Pristine MnTe is a p-type semiconductor with an average hole concentration of 10 19 cm 3 . Many dopants like Sodium, Copper and Sulphur were incorporated in the MnTe and their thermoelectric properties were studied. Antimony is an ideal dopant to alter the thermoelectric properties. Compounds belonging to the series Mn 1x Sb x Te with (x ¼ 0, 0.005, 0.01, 0.015, 0.02) were prepared using a combination of High Energy Ball Milling (HEBM), melt quenching and hot press techniques. Structural, electrical and thermo- electric properties of these compounds were determined. Carrier concentration and mobility were measured by Hall measurement techniques. Charge carrier concentration increases with Sb doping while mobility and effective mass decreases. Seebeck coefficient and electrical conductivity were measured in the temperature range 100 Ke730 K, and thermal conductivity was evaluated in the temperature range 100 Ke300 K. The power factor and figure of merit (ZT) were also estimated. The highest power factor achieved is at 730 K and is 1768mWm 1 K 2 for Mn 0:98 Sb 0:02 Te. The highlight of the present study is the rise in electrical conductivity and reduction in the thermal conductivity with Sb doping. © 2020 Elsevier B.V. All rights reserved. 1. Introduction The relevance of developing alternative eco-friendly technolo- gies for energy conversion need not be over emphasized in the present context. Among various technologies for energy conver- sion, thermoelectrics occupies an important position [1]. Thermo- electric materials convert thermal energy into electrical energy and vice versa [1e5]. The conversion efficiency of a material is deter- mined by a dimensionless quantity called the figure of merit ZT ZT ¼ S 2 T rt (1) where r is the electrical resistivity, S is the Seebeck coefficient, and t is the thermal conductivity, and T is the absolute temperature. Thermal conductivity consists of two parts, lattice thermal con- ductivity (t lat ) and electronic thermal conductivity (t el )[2,6e8]. High power factor  PF ¼ S 2 r ! is linked to low thermal conductivity and is crucial to accomplish high ZT values [9e12]. To enhance the power factor as well as ZT of bulk materials, band engineering [13, 14] is adopted. Low energy filtering effect also plays an impor- tant role [15], while nanostructuring [9] helps to reduce thermal conductivity [16, 17]. Lead telluride and bismuth telluride have been investigated extensively for potential thermoelectric applications in the 60s and 70s. In that, lead telluride assume significance due to its high conversion efficiency in the mid-temperature region [18, 19]. Though, both lead telluride and bismuth telluride are considered to be good materials for thermoelectric applications, the presence of lead has prompted scientists and engineers to scout for lead-free thermoelectric materials. The approach has been multi pronged in the sense that some concentrated on developing new materials possessing high ZT such as sulphides [20,21], selenides [22,23], oxides [24,25] skutterudite type structures [26,27], half heusler alloys [28], and PbTe [29] type structures. The other approach has been to modify the existing materials either by nanostructuring or by substitution or both to modify the band and then tailor electrical conductivity, Seebeck coefficient, and thermal conductivity [30,31]. * Corresponding author. Department of Physics, Cochin University of Science and Technology, Cochin, 682022, Kerala, India. E-mail address: mraiyer@yahoo.com (M.R. Anantharaman). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2020.155374 0925-8388/© 2020 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 836 (2020) 155374