Microstructure and thermoelectric properties of p-type bismuth antimony telluride nanowires synthetized by template electrodeposition in polycarbonate membranes

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

The recent advancements in thermoelectric materials are largely credited to two factors, namely established physical theories and advanced materials engineering methods. The developments in the physical theories have come a long way from the "phonon glass electron crystal" paradigm to the more recent band convergence and nanostructuring, which consequently results in drastic improvement in the thermoelectric figure of merit value. On the other hand, the progresses in materials fabrication methods and processing technologies have enabled the discovery of new physical mechanisms, hence further facilitating the emergence of high-performance thermoelectric materials. In recent years, many comprehensive review articles are focused on various aspects of thermoelectrics ranging from thermoelectric materials, physical mechanisms and materials process techniques in particular with emphasis on solid state reactions. While bottom-up approaches to obtain thermoelectric materials have widely been employed in thermoelectrics, comprehensive reviews on summarizing such methods are still rare. In this review, we will outline a variety of bottom-up strategies for preparing high-performance thermoelectric materials. In addition, state-of-art, challenges and future opportunities in this domain will be commented.

Electron-Transparent Thermoelectric Coolers Demonstrated with Nanoparticle and Condensation Thermometry

More efficient thermoelectric devices would revolutionize refrigeration and energy production, and low-dimensional thermoelectric materials are predicted to be more efficient than their bulk counterparts. But nanoscale thermoelectric devices generate thermal gradients on length scales that are too small to resolve with traditional thermometry methods. Here we fabricate, using single-crystal bismuth telluride (Bi₂Te₃) and antimony/bismuth telluride (Sb_2-xBi_xTe₃) flakes exfoliated from commercially available bulk materials, functional thermoelectric coolers (TECs) that are only 100 nm thick. These devices are the smallest TECs ever demonstrated by a factor of 10⁴. After depositing indium nanoparticles to serve as nanothermometers, we measure the heating and cooling produced by the devices with plasmon energy expansion thermometry (PEET), a high-spatial-resolution, transmission electron microscopy (TEM)-based thermometry technique, demonstrating a ΔT = -21 ± 4 K from room temperature. We also establish proof-of-concept for condensation thermometry, a quantitative temperature-change mapping technique with a spatial precision of ≲300 nm.

Electrodeposition of V-VI Nanowires and Their Thermoelectric Properties

Nanostructuration is an intensive field of research due to the appearance of interesting properties at the nanoscale. For instance, in thermoelectricity the most outstanding improvements obtained lately are related to phenomena that appear as a result of nano-engineering different materials. The thermoelectric effect is the direct conversion from temperature gradients into electricity and vice versa. When going to low dimensions, for example in the particular case of thermoelectric nanowires, the transport properties of phonons are modified with respect to those found in bulk leading to a higher thermoelectric figure of merit z. In more detail, this review tries to compile some of the landmarks in the electrodeposition of Bi₂Te₃-based nanowires. We will focus on the achievements using different templates, electrolytes and deposition modes. We will also summarize the measurements performed in those nanowires and the main conclusions that can be extracted from the published works. Finally, an update of nanowire-based thermoelectric generators is also included.

Effect of deposition potential and concentration of electroactive substances on Bi2Te3 nanowires fabricated by electrochemical method

In this paper, Bi₂Te₃ nanowires were prepared in anodized aluminum oxide template by electrochemical deposition. The morphological microstructural and electrical resistance characteristics of the nanowires were discussed to reveal the effect of deposition potential and electroactive substance (HTeO₂ ⁺) concentration. According to the electrode dynamics formula, it is found that the increase of electrode potential leads to the decrease of deposition current, so that deposition rate of nanowires decreases. At the same time, the deposition current controlled by diffusion in the mass transport process will have a maximum value with the increasing of deposition time. The deposition potential determines the favorable crystal plane for nanowires growth by the selection of proper surface energy. The temperature dependence of resistances in Bi₂Te₃ nanowires fabricated under different concentration of HTeO₂ ⁺ reveals the transformation of the carriers' main scattering mechanism. This study could provide a better understanding of the deposition process of Bi₂Te₃ nanowires.