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Thermoelectric (TE) materials are utilized as power generators or coolers in several applications, such as mini-power generation systems and micro-coolers, CCD technology, and infrared detectors. The TE dimensionless figure-of-merit, ZT, is expressed as S2Tσ/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity. Bismuth telluride is the state-of-the-art TE material for cooling applications with a ZT, of ~1 at 300K. In our previous research, we have demonstrated that nanostructured TE materials have resulted in a significant reduction of the thermal conductivity, κ, thus enhancing ZT. Recent theoretical considerations by Dresselhaus et al., indicate that low-dimensional systems such as quantum-well superlattice structures (2D) and quantum wires (1D) might enhance TE properties compared to their bulk counterpart. The enhancement of ZT is achieved by greatly scattering phonons at the interface, leading to a reduction of the phonon thermal conductivity without sacrificing electrical conductivity.
In this study we report on the fabrication of 1-D bismuth telluride nanowires by DC electrochemical deposition into porous anodic alumina membranes (AAM). A typical 3 electrode electro-deposition cell is employed with a Ag/AgCl reference electrode (SSCE). Acidic electrolytic solutions containing Bi(III) and Te(IV) salts with given concentrations were used as electrolysis bath. Bi2Te3 alloy could be directly obtained by both galvanostatic/potentiostatic electrodeposition. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and XRD have been used to characterize the physical and chemical properties of the nanowires. Stoichiometric Bi2Te3 was obtained both galvanostatically and potentiostatically with a preferred crystal growth direction of (110). Uniform nanowires were obtained with high aspect ratio (>100) and high filling ratio (>70%) of the membrane. The effect of different electrochemical deposition parameters on composition, morphology, and crystal phases was studied. Different physical and thermoelectric properties of the fabricated nanowires and nanowires array are reported.
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