Melt spinning: A rapid and cost effective approach over ball milling for the production of nanostructured p-type Si 80 Ge 20 with enhanced thermoelectric properties Riya Thomas a , Ashok Rao a, * , Nagendra S. Chauhan b , Avinash Vishwakarma b , Niraj Kumar Singh c , Ajay Soni c a Department of Physics, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, India b Advance Materials and Devices, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India c School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175005, India article info Article history: Received 31 July 2018 Received in revised form 28 November 2018 Accepted 30 November 2018 Available online 11 December 2018 Keywords: SiGe Thermoelectric properties Ball milling Melt spinning Spark plasma sintering Figure-of-merit abstract In this work, we have adopted melt-spinning technique followed by spark plasma sintering (SPS) to synthesize a p-type nanostructured Si 80 Ge 20 alloy. To illustrate the impact of the technique, the results are compared with that of prepared by ball milling and subsequent SPS. The room temperature XRD of the alloys prepared by both the techniques confirms that they crystallize with diamond-like cubic structure of space group Fd 3m. The remarkably decreased thermal conductivity and increased Seebeck coefficient results in a higher ZT of melt spun sample (nearly ~46% higher at room temperature) as compared to the ball milled sample. The short preparation time of melt spun p-type Si 80 Ge 20 alloy coupled with its enhanced thermoelectric performance indicate that this technique provides a novel strategy to improve the thermoelectric properties of SiGe alloys thus making this synthesis process of interest for commercial purposes. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Thermoelectric materials (TE) belong to the category of renewable energy resources facilitating the inter-conversion be- tween thermal and electrical energy on the basis of thermoelectric effects viz. Seebeck and Peltier effects [1 ,2]. The elevating concerns related to the increase in energy demands, coupled with the environmental pollution due to the combustion of fossil fuels, have led to the transition towards a search for clean, renewable, and cost effective energy sources. On this account, TE materials have gained great attention as potential candidates for both energy harvesting and cooling applications. Thermoelectric power generators work on the principle of Seebeck effect which allows the conversion of a temperature difference into electricity without the involvement of any moving parts or noisy mechanisms [2e4]. The performance of TE materials is dependent on the interplay of their electrical parameters (Seebeck coefficient S and electrical conductivity s) and thermal parameter (total thermal conductivity, k ¼ k e þ k l , where k e is the electronic component and k l is the lattice component contributing to k). Mathematically it is evaluated by a dimensionless quantity called figure of merit, ZT which at absolute temperature T is given by Refs. [1 ,2]; ZT ¼ S 2 s k T (1) Higher the ZT, better is the efficiency of the TE materials and thus optimizing ZT has been of crucial importance for the last several decades. The TE materials comprise of a wide variety of materials ranging from semimetals, semiconductors and ceramics, having various crystalline forms like monocrystals, polycrystals and nanocomposite [5e8]. They can also have different dimensions like bulk, thin films, nanowires and nanoclusters [9, 10]. TE materials can be classified depending on the temperature range of their ap- plications. For low and near room temperature applications, CsBi 4 Te 6 and Bi 2 Te 3 show thermoelectric properties of great importance and have been investigated since 1950's [6,7 , 11e 15]. In fact Bi 2-x Sb x Te 3 is the most commonly used TE material in * Corresponding author. E-mail address: a.rao@manipal.edu (A. Rao). 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.2018.11.414 0925-8388/© 2018 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 781 (2019) 344e350