Thermoelectric properties of spark plasma sintered lead telluride nanocubes

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Sivaiah Bathula, Bhasker Gahtori, Avanish Kumar Srivsatava, and Ajay Dhar CSIR-Network of Institutes for Solar Energy, Materials Physics and Engineering Division, CSIR-National Physical Laboratory, New Delhi 110012, India

Amirthapandian Sankarakumar and Binaya Kumar Panigrahi Materials Physics Division, Materials Science Group, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, India

Sriparna Bhattacharya,b) Ramakrishna Podila, and Apparao M. Rao Departments of Physics and Astronomy, Clemson Nanomaterials Center, COMSET, Clemson University, Clemson, South Carolina 29634, USA (Received 25 May 2015; accepted 15 July 2015)

We report a cost-effective, surfactant-free, and scalable synthesis technique for lead telluride (PbTe) nanocubes by a chemical precipitation method. The high-resolution transmission electron microscopy studies indicated the evolution of nucleation centers (spherical) into nanocubes with the addition of the Pb and Te atoms. The spark plasma sintered PbTe nanocubes exhibited an enhanced Seebeck coefficient, S . 1400 lV, higher than the reported values of the bulk PbTe over an extended temperature range of 300–425 K, and a moderate electrical conductivity, r ; 8000 S/m at 300 K. A significant reduction in the lattice thermal conductivity was observed due to effective phonon scattering from the presence of numerous interfaces introduced by nanostructuring. The resulting figure-of-merit (ZT) ; 0.45 at 300 K is higher than the reported values at this temperature in other PbTe nanostructures. Moreover, a moderate thermoelectric compatibility factor makes the PbTe nanocubes a potential candidate for green energy generation.  I. INTRODUCTION

As the global energy consumption continues to increase rapidly, we are compelled to find alternative renewable energy generation and storage resources and make their production economically viable to displace the use of fossil fuels.1,2 While solar and wind energy harvesting could be directly integrated into the grid, thermoelectric (TE) materials that convert waste heat into electricity, can serve as an excellent energy resource for low-power electronic devices, such as automotive TE generators and radio communications.3,4 However, limited efficiency, dissimilar compatibility factors between the n- and p-type TE materials,5 and the lack of inexpensive scalable methods to manufacture TE materials have limited their use in power generation.4 The performance of TE materials is strongly associated with the dimensionless figure of merit (ZT) which is defined as

ZT ¼

 S2 r T j

;

ð1Þ

Contributing Editor: Terry M. Tritt Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2015.227

where S is the Seebeck coefficient, r is the electrical conductivity, and j is the total thermal conductivity (j 5 jl 1 je; jl and je are the lattice and electronic thermal conductivities, respectively). High electrical conductivity (corresponding to low Joule heating losses, or electron crystal behavior), large Seebeck coef

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