Thermoelectric properties of hot pressed CZTS micro spheres synthesized by microwave method
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.189
Thermoelectric properties of hot pressed CZTS micro spheres synthesized by microwave method Sarita Devi Sharma1 and Sonnathi Neeleshwar 1 1
University School of Basic & Applied Sciences, GGS Indraprastha University, New Delhi, India
email: [email protected]
ABSTRACT
Microwave synthesis of Copper Zinc Tin Sulphide (CZTS) sphere like particles has been demonstrated. The structural and morphological properties of CZTS particles are characterized by XRD, SEM and Raman spectroscopy and subsequently thermoelectric properties are investigated. XRD results of prepared powder sample matches well with tetragonal crystal structure of CZTS bulk. No other impurity phase has been detected from the XRD analysis. Raman spectrum further confirms the formation of single phase CZTS with characteristics peak for CZTS at 334.1 cm-1. SEM studies reveal that the CZTS particles are spherical in shape with uniform sizes of ~ 250-350 nm. Hot pressed CZTS system shows a power factor ~21 µW/mK2 and ZT~ 0.024 at 623 K. Significant enhancement in the Figure of merit for CZTS system is observed in comparison to reported nanostructures of the same system may be due to increased electrical conductivity.
INTRODUCTION Sustainable energy resources are getting more attention these days due to the higher energy demand worldwide. One of such energy resources is from utilization of waste heat from surroundings. Thermoelectric materials have the capability of tapping this abundant waste heat into useful electrical energy by selecting suitable thermoelectric module [1, 2]. The efficiency of thermoelectric materials is judged by a dimensionless quantity, ZT= σS2T/k, where σ is electrical conductivity, S is Seebeck coefficient and k is the thermal conductivity. All these properties of a material are interdependent and are further influenced by numerous factors [3]. The conventional thermoelectric materials are mainly categorized on the basis of their temperature of operation and generally consist of toxic or less abundant materials i,e Pb, Te, Si etc. thus their civil applications are greatly limited [4]. Nowadays, the development of cost effective and eco friendly thermoelectric materials is being explored by researchers e.g Copper based chalcogenides (Cu2X, Cu2ZnSnX etc. where X=S, Se) [5]. Conventional thermoelectric materials exhibit a small band gap which leads to bipolar effect that can reduce the thermoelectric properties. The quaternary compounds like CZTX (X=Se, S) can eliminate the bipolar effect due to large band gap and thermal conductivity is also low because of their complex structures [6, 7]. CZTS is a type of quaternary Copper compound which consist of low cost, earth abundant and non-toxic elements. CZTS material applications are in the field of photovoltaics and thermoelectrics [8, 9]. There are very few reports on the thermoelectric properties of CZTS thermoelectric materials due to the low power factor, which is due to the high resistivity of the material [9, 10]. T
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