Abstract
Melt-spinning (MS) has been reported as a promising tool to tailor the microstructure of bulk thermoelectric materials leading to enhanced thermoelectric performances. Here, we report on a detailed characterization of p-type Bi0.48Sb1.52Te3 ribbons produced by melt-spinning. The microstructure of the melt-spun ribbons has been studied by means of X-ray diffraction, scanning and transmission electron microscopy (TEM). The analyses indicate that the ribbons are highly-textured with a very good chemical homogeneity. TEM reveals clear differences in the microstructure at large and short-range scales between the surface that was in contact with the copper wheel and the free surface. These analyses further evidence the absence of amorphous regions in the melt-spun ribbons and the precipitation of elemental Te at the grain boundaries. Low-temperature electrical resistivity and thermopower measurements (20–300 K) carried out on several randomly-selected ribbons confirm the excellent reproducibility of the MS process. However, the comparison of the transport properties of the ribbons with those of bulk polycrystalline samples of the same initial composition shows that MS leads to a more pronounced metallic character. This difference is likely tied to changes in deviations from stoichiometry due to the out-of-equilibrium conditions imposed by MS.
Highlights
Thermoelectric materials provide a versatile, environmentally-friendly way for generating electric power from waste heat or for Peltier cooling [1,2]
A more widespread use of thermoelectric materials is tied to the identification of novel families of materials exhibiting a high dimensionless thermoelectric figure of merit: ZT = α2 T/ρκ where α is the thermopower, ρ is the electrical resistivity, κ is total the thermal conductivity and T is the absolute temperature; or to the optimization of the thermoelectric properties of state-of-the-art materials [1,2,3]
For thermoelectric applications near room temperature, solid solutions of bismuth telluride Bi2 Te3 with the isomorphous compounds
Summary
Thermoelectric materials provide a versatile, environmentally-friendly way for generating electric power from waste heat or for Peltier cooling [1,2]. Starting from raw materials, MS produces ribbons, flakes or foils, which are in an out-of-equilibrium state due to the high quenching rate leading to particular microstructures and physical properties This technique has been the subject of studies from a mathematical point of view [36]. Because melt-spun ribbons are subsequently consolidated to obtain bulk dense specimens, a detailed investigation of their microstructure-properties relationships is essential to better understand the influence of the MS process on the thermoelectric properties of Bi2 Te3 -based materials. Our results evidence that the melt-spun ribbons show a more pronounced metallic character with respect to bulk polycrystalline samples of the same initial composition, which highlights the extreme sensitivity of the Bix Sb2−x Te3 compounds to the synthetic process used We attribute this difference to modifications in the deviations from stoichiometry as a result of the strong out-of-equilibrium conditions achieved in the MS process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
