High Seebeck Coefficient BiSbTe Nanowires

Abstract

Bismuth antimony telluride ͑BiSbTe͒ nanowires were electrodeposited at constant potentials into polycarbonate templates from a tartaric-nitric acid electrolyte. Optimum deposition potentials were obtained from polarization and compositional analysis. X-ray diffraction analysis showed a preferential ͑015͒ orientation for the nanowires. The Bi 2 Sb 0.6 Te 3 nanowire sample deposited at Ϫ150 mV showed a high Seebeck coefficient ͑S͒ of −630 V/K.Concerns over the depleting fossil fuels and increasing global warming threat stimulated the researchers to develop efficient thermoelectric materials, defined by the figure of merit as ZT = S 2 T/k, where S is the Seebeck coefficient, is electrical conductivity, T is the absolute temperature, and k is thermal conductivity. 1 The ZT of the current bulk materials is limited to 1; 2 however, a value higher than 3 is required to compete with conventional energy techniques. Increasing the thermoelectric power factor ͑S 2 ͒ and decreasing the thermal conductivity are the two main approaches to increase ZT. In superlattice Bi 2 Te 3 /Sb 2 Te 3 thin films, a high ZT of 2.4 was obtained mainly by the decreased lattice thermal conductivity. 3 Taking into account the improved density of states resulting in higher power factors and decreased phonon thermal conductivity due to surface scattering, Dresselhaus's group 2,4 predicted an even higher ZT for one-dimensional nanostructures. Also, experimental results showed 5 that BiTe nanowires have lower thermal conductivity than their bulk counterparts.Stacy's group 6 was the first to report electrodeposition of BiSbTe nanowires in porous alumina templates using a tartaric-nitric acid based electrolyte and proposed different mechanisms for the reduction of BiSbTe alloys following the overall reaction Del Frari et al. 7,8 studied the optimum conditions for electrodeposition of Bi 0.5 Sb 1.5 Te 3 alloys from a tartaric-perchloric acid bath and measured a thin-film power factor of 600 WK −2 m −1 . Xiao et al. 9 electrodeposited ͑Bi 0.3 Sb 0.7 ͒ 2 Te 3 and Bi 1.8 Sb 0.1 Te 3.1 nanowires in polycarbonate template and described their semiconducting nature from the temperature-dependent current-voltage plots. Although few articles are available on the electrodeposition of BiSbTe nanowires, 6-9 there is a need for their thermoelectric characterization. Our current research focuses on achieving higher Seebeck coefficients, by optimizing the alloy composition, using electrodeposited of BiSbTe nanostructures. To the best of our knowledge, the reported Seebeck coefficients here are the highest values among the electrodeposited BiTe alloy family ͑BiSbTe and BiSeTe͒ materials. 10-12 ExperimentalBiSbTe nanowires were electrodeposited into polycarbonate membranes using a Solartron 1287 function generator at constant potentials and room temperature from a tartaric-nitric acid based electrolyte. Being difficult to dissolve, Sb 2 O 3 was treated with tartaric acid as a complexing agent to increase its solubility in water, and the obtained solution was mixed with...

Structure and Thermoelectric Properties of Bi2−xSbxTe3 Nanowires Grown in Flexible Nanoporous Polycarbonate Templates

“…Instead, in this work, we have presented measurements of the thermoelectric performance of embedded nanowire arrays which can be directly incorporated in real life applications. The thermoelectric parameters evaluated in this way are lower than the literature reports of single nanowires (see Supporting Information ), due to higher probability of encountering a small fraction of defective nanowires containing imperfections such as anti-site defects, Te-rich nano-nuggets, accidental Au doped regions, etc., which affect the Seebeck coefficient and thermoelectric power factor [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Nevertheless, evaluation of thermoelectric performance of the as-grown template-embedded nanowires offers valuable insight into their applicability in thermoelectric devices.…”

Thermoelectric devices based on one-dimensional nanostructures

“…For BiSbTe alloy, the atomic ratio affected the Seebeck coefficient. The Bi 2 Sb 0.6 Te 3 NWs, electrodeposited at constant potential of À150 mV, had the highest Seebeck coef-cient of À630 mV K À1 at 300 K. 24 Due to potential applications in thermoelectric elds, several methods have been developed to fabricate 1D nanostructures of Bi-Te and related alloys, such as template-assisted electrodeposition, hydrothermal methods, on-lm formation of NWs (OFF-ON), galvanic displacement and so on. The up to date and representative fabrication approaches will be discussed herein.…”

“…In order to obtain ordered 1D nanostructures, templates have been usually used in electrodeposition, such as anodic aluminium oxide (AAO) template and porous polymer membranes. 24,26,27 The AAO template is commonly used for the reasons (1) it is electrically insulating and reasonably robust, (2) the pore diameters are easily adjusted, (3) the pore density and aspect ratio could be high. 28 The size of the pores in the AAO determines the diameter of the NWs.…”

Advancing Thermoelectric Materials: A Comprehensive Review Exploring the Significance of One-Dimensional Nano Structuring

“…Polycrystalline Bi NWs with a 74–255 nm diameter demonstrate 18–78 times lower thermal conductivities than bulk Bi NWs throughout the same temperature range [ 246 ]. Single crystalline Bi NWs with 40 nm diameter have extremely low lattice thermal conductivity of 0.13 Wm −1 K −1 at 77 K [ 247 ], while the Bi 2 Sb 0.6 Te 3 NWs showed a high Seebeck coefficient of −630 μVK −1 at 300 K [ 248 ]. Figure 13 a shows an SEM image of the synthesis of Bi nanowire arrays by physical vapour deposition.…”