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For decades, the V2VI3 compounds, specifically p-type Bi2-xSbxTe3 and n-type Bi2Te3-xSex, have remained the cornerstone of commercial thermoelectric solid-state cooling and power generation near room temperature. However, a long-standing problem in V2VI3 thermoelectrics is that n-type Bi2Te3-xSex is inferior in performance to p-type Bi2-xSbxTe3 near room temperature, restricting the device efficiency. In this work, we developed high-performance n-type Bi2-xSbxTe3, a composition long thought to only make good p-type thermoelectrics, to replace the mainstream n-type Bi2Te3-xSex. The success arises from the synergy of the following mechanisms: (i) the donorlike effect, which produces excessive conduction electrons in Bi2Te3, is compensated by the antisite defects regulated by Sb alloying; (ii) the conduction band degeneracy increases from 2 for Bi2Te3 and Bi2Te3-xSex to 6 for Bi2-xSbxTe3, favoring high Seebeck coefficients; and (iii) the larger mass fluctuation yet smaller electronegativity difference and smaller atomic radius difference between Bi and Sb effectively suppresses the lattice thermal conductivity and retains decent carrier mobility. A state-of-the-art zT of 1.0 near room temperature was attained in hot deformed Bi1.5Sb0.5Te3, which is higher than those for most known n-type thermoelectric materials, including commercial Bi2Te3-xSex ingots and the popular Mg3Sb2. Technically, building both the n-leg and p-leg of a thermoelectric module using similar chemical compositions has key advantages in the mechanical strength and the durability of devices. These results attested to the promise of n-type Bi2-xSbxTe3 as a replacement of the mainstream n-type Bi2Te3-xSex near room temperature.

Half-Heusler (HH) phases have garnered much attention as thermally stable and non-toxic thermoelectric materials for power conversion. The most studied alloys to date utilize Hf, Zr, and Ti as the base components. These alloys can achieve a moderate dimensionless figure of merit, ZT, near 1. Recent studies have advanced the thermoelectric performance of HH alloys by employing nanostructures and novel compositions to achieve larger ZT, reaching as high as 1.5. Herein, we report that traditional alloying techniques applied to the conventional HfZr-based half-Heusler alloys can also lead to exceptional ZT. Specifically, we present the well-studied p-type Hf0.3Zr0.7CoSn0.3Sb0.7, previously reported to have a ZT~0.8, resonantly doped with less than 1 at. % metallic Al on the Sn/Sb site, touting a remarkable ZT near 1.5 at 980 K. This is achieved through a significant increase in power factor, by ~65%, and a notable but smaller decrease in thermal conductivity, by ~13%, at high temperatures. These favorable thermoelectric properties are discussed in terms of a local anomaly in the density of states near the Fermi energy designed to enhance the Seebeck coefficient, as revealed by first-principles calculations, as well as the emergence of a highly heterogeneous grain structure that can scatter phonons across different length scales, effectively suppressing the thermal conductivity. Consequently, the effective mass is significantly enhanced from ~ 7 to 10me within a single parabolic band model, consistent with the result from first-principles calculations. The discovery of high ZT in a commonly studied half-Heusler alloy through a conventional and non-complex approach opens a new path for further discoveries in similar types of alloys. Furthermore, it is reasonable to believe that the study will reinvigorate effort in exploring high thermoelectric performance in conventional alloy systems., Comment: To be published in Materials Today Physics

Other than facilitating phase separation that is often the case, large atomic size mismatch may elicit bulk metallic glasses, crystalline line compounds, or solid solution-like single phases of matter with exquisite atomic structures and application-pertinent properties.

Understanding the mechanisms of proton conduction at the interface of materials enables the development of a new generation of protonic ceramic conductors at low temperatures (150 °C) through water absorption and proton transport on the surface and grain boundaries. Conductivity measurements under Ar-3% H

For decades, the V

The net radial flow velocity of gas is an important parameter for understanding galaxy evolution. It is difficult to measure in the presence of the elliptical orbits of an oval distortion because the mathematical model describing the observed velocity is degenerate in the unknown velocity components. A method is developed in this paper that breaks the degeneracy using additional information about the angular frequency of the oval distortion. The method is applied to the neutral hydrogen in the oval distortion of NGC 4736. The neutral hydrogen is flowing inward at a mean rate of -6.1 $\pm$ 1.9 km s$^{-1}$. At this rate, it takes 400 Myr, or 1.7 rotations of the oval distortion, for the neutral hydrogen to travel the 2.5 kpc from the end to the beginning of the oval distortion. The mean mass flow rate of the neutral hydrogen in this region is -0.25 $\pm$ 0.11 $M_\odot$ yr$^{-1}$, which is similar to estimates for the star formation rate reported in the literature., Accepted for publication in The Astrophysical Journal

A synergy of fine-tuning the carrier concentration and implementing scatter of heat-carrying phonons is vital to the thermoelectric study of narrow bandgap semiconductors. In this work, we adopted a synergistic charge-balanced compensation-doping approach derived from the interplay between heterovalent Sb dopants and Sn vacancies in narrow band gap semiconductor SnTe, a lead-free alternative to the classic thermoelectric material PbTe. Specifically, we designed a composition series of Sn1-xSb2x/3Te (0 ≤ x ≤ 0.20 in steps of 0.02), in which every three Sn2+ are substituted by two Sb3+ and one Sn vacancy. To the first order, such chemical composition does not contribute net charge carriers in the context of electron counting and also ensures that the composition of the primary phase is not altered by the formation of secondary phase Sb2Te3, which greatly simplifies the data analysis. Interestingly, we found that the measured carrier concentration gradually reduced with increasing Sb content and in turn increased the Seebeck coefficient. Meanwhile, the coexistence of Sb dopants and Sn vacancies effectively scattered heat-carrying phonons at elevated temperatures. Consequently, a peak ZT value of ~1.1 at 873K was achieved in the x = 0.12 sample. These results offer a new avenue for thermoelectric study of narrow bandgap semiconductors.

Herein the effect of Co element doping on the thermoelectric properties of n-type Bi2(Te0.97Se0.03)3 alloys fabricated by a melting synthesis technique followed by spark plasma sintering was reported. The micro-morphology and composition of the specimens was characterized by means of X-ray diffraction and scanning electron microscopy. The electrical and thermal properties of (Bi1-xCox)2(Te0.97Se0.03)3 with x = 0%, 2%, 4% and 8% were measured from 298K to 473K. We found that (i) the micro-scale secondary phase CoTe2 was embedded into the matrix due to the low solubility of Co element; (ii) Co doping generally improved the effective mass due to the scattering by local magnetic moments carried by Co ion and practically retained the carrier concentration, thereby yielding the higher Seebeck coefficient; (iii)both the electronic and lattice thermal conductivity decreased simultaneously by introducing the hierarchical defects (point defects and the micro-scale defects). Specifically, the x = 8% sample obtained a minimum thermal conductivity ~1.26 Wm−1K−1 at 398K. This results in a maximum ZT value of ~0.77, approximately ~20% higher than that of pristine Bi2(Te0.97Se0.03)3.

Compartmentalisation is a defining feature of biological processes. Within eukaryotic cells, organelles serve as segregated microenvironments for specific biochemical processes. These microenvironments allow distinct chemical environments to be maintained within the cell and concentrate enzymes involved in catalytic cycles in the same space. This concentration of enzymes and substrates within a small segregated environment contributes to the great efficiency of biochemical processes. I aim to investigate the potential of a novel artificial lipid membrane system, the droplet interface bilayer (DIB), as a platform for a spatially segregated compartmentalised nanoreactor. DIB technology serves as a simple method for producing small aqueous compartments bounded by lipid membranes. The incorporation of membrane transport proteins between the aqueous compartments will allow distinct chemical environments to be maintained and for the controlled separation of substrates and products. The nanoreactor design will aim to recreate the segregated microenvironments and enhanced catalytic efficiencies found in biological processes in a synthetic setting.