The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the dominant carrier type. Here, we report a very rapid (2 min) and high yield (>8 g/batch) synthetic method using microwave-assisted heating, for the controlled growth of Bi_2–xSb_xTe₃ (x: 0–2) nanoplatelets. Resultant materials exhibit a high crystallinity and phase purity, as characterized by XRD, and platelet morphology, as revealed by SEM. Surface chemistry of as-made materials showed a mixture of metallic and oxide phases, as evidenced by XPS. Zeta-potential analysis exhibited a systematic change of isoelectric point as a function of the material composition. As-made materials were directly sintered into pellets by using spark plasma sintering process. TE performance of Bi_2−xSb_xTe₃ pellets were studied, where the highest ZT values of 1.04 (at 440 K) for Bi₂Te₃ and 1.37 (at 523 K) for Sb₂Te₃ were obtained, as n- and p-type TE materials. The presented microwave-assisted synthesis method is energy effective, a truly scalable and reproducible method, paving the way for large scale production and implementation of towards large-area TE applications.

Scalable synthetic strategies for high-quality and reproducible thermoelectric (TE) materials is an essential step for advancing the TE technology. We present here very rapid and effective methods for the synthesis of nanostructured bismuth telluride materials with promising TE performance. The methodology is based on an effective volume heating using microwaves, leading to highly crystalline nanostructured powders, in a reaction duration of two minutes. As the solvents, we demonstrate that water with a high dielectric constant is as good a solvent as ethylene glycol (EG) for the synthetic process, providing a greener reaction media. Crystal structure, crystallinity, morphology, microstructure and surface chemistry of these materials were evaluated using XRD, SEM/TEM, XPS and zeta potential characterization techniques. Nanostructured particles with hexagonal platelet morphology were observed in both systems. Surfaces show various degrees of oxidation, and signatures of the precursors used. Thermoelectric transport properties were evaluated using electrical conductivity, Seebeck coefficient and thermal conductivity measurements to estimate the TE figure-of-merit, ZT. Low thermal conductivity values were obtained, mainly due to the increased density of boundaries via materials nanostructuring. The estimated ZT values of 0.8–0.9 was reached in the 300–375 K temperature range for the hydrothermally synthesized sample, while 0.9–1 was reached in the 425–525 K temperature range for the polyol (EG) sample. Considering the energy and time efficiency of the synthetic processes developed in this work, these are rather promising ZT values paving the way for a wider impact of these strategic materials with a minimum environmental impact.

Gas sensitive structures made of nanowires exhibit extremally large specific surface area, and a great number of chemically active centres that can react with the ambient atmosphere. This makes the use of nanomaterials promising for super sensitive gas sensor applications. Monoclinic β-Ga₂O₃ nanowires (NWs) were synthesized from metallic gallium at atmospheric pressure in the presence of nitrogen and water vapor. The nanowires were grown directly on interdigitated gold electrodes screen printed on Al₂O₃ substrates, which constituted the gas sensor structure. The observations made with transmission electron microscope (TEM) have shown that the nanowires are monocrystalline and their diameters vary from 80 to 300 nm with the average value of approximately 170 nm. Au droplets were found to be anchored at the tips of the nanowires which may indicate that the nanowires followed the Vapor–Liquid–Solid (VLS) mechanism of growth. The conductivity of β-Ga₂O₃ NWs increases in the presence of volatile organic compounds (VOC) even in the temperature below 600 °C. The gas sensor based on the synthesized β-Ga₂O₃ NWs shows peak sensitivity to 100 ppm of ethanol of 75.1 at 760 °C, while peak sensitivity to 100 ppm of acetone is 27.5 at 690 °C.

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of $$\pi ^\pm $$π ± , $$K^\pm $$K ± , p and $$\bar{p}$$p ¯ produced in $$^{40}\hbox {Ar+}^{45}\hbox {Sc}$$40 Ar+ 45 Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A $$\text{ Ge }\hspace{-1.00006pt}\text{ V }\!/\!c$$Ge V / c . The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the $$K^\pm $$K ± / $$\pi ^\pm $$π ± ratios as well as of inverse slope parameters of the $$K^\pm $$K ± transverse mass distributions are placed in between those found in inelastic $$p+p$$p + p and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.