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31.
Subtle Roles of Sb and S in Regulating the Thermoelectric Properties of N‐Type PbTe to High Performance 下载免费PDF全文
Gangjian Tan Constantinos C. Stoumpos Si Wang Trevor P. Bailey Li‐Dong Zhao Ctirad Uher Mercouri G. Kanatzidis 《Liver Transplantation》2017,7(18)
A high ZT (thermoelectric figure of merit) of ≈1.4 at 900 K for n‐type PbTe is reported, through modifying its electrical and thermal properties by incorporating Sb and S, respectively. Sb is confirmed to be an amphoteric dopant in PbTe, filling Te vacancies at low doping levels (<1%), exceeding which it enters into Pb sites. It is found that Sb‐doped PbTe exhibits much higher carrier mobility than similar Bi‐doped materials, and accordingly, delivers higher power factors and superior ZT . The enhanced electronic transport is attributed to the elimination of Te vacancies, which appear to strongly scatter n‐type charge carriers. Building on this result, the ZT of Pb0.9875Sb0.0125Te is further enhanced by alloying S into the Te sublattice. The introduction of S opens the bandgap of PbTe, which suppresses bipolar conduction while simultaneously increasing the electron concentration and electrical conductivity. Furthermore, it introduces point defects and induces second phase nanostructuring, which lowers the lattice thermal conductivity to ≈0.5 W m?1 K?1 at 900 K, making this material a robust candidate for high‐temperature (500–900 K) thermoelectric applications. It is anticipated that the insights provided here will be an important addition to the growing arsenal of strategies for optimizing the performance of thermoelectric materials. 相似文献
32.
Functional characterization of domains in AtTRB1, a putative telomere-binding protein in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Telomeres are nucleoprotein structures ensuring the stability of eukaryotic chromosome ends. Two protein families, TRFL (TFL-Like) and SMH (Single-Myb-Histone), containing a specific telobox motif in their Myb domain, have been identified as potential candidates involved in a functional nucleoprotein structure analogous to human "shelterin" at plant telomeres. We analyze the DNA-protein interaction of the full-length and truncated variants of AtTRB1, a SMH-family member with a typical structure: N-terminal Myb domain, central H1/5 domain and C-terminal coiled-coil. We show that preferential interaction of AtTRB1 with double-stranded telomeric DNA is mediated by the Myb domain, while the H1/5 domain is involved in non-specific DNA-protein interaction and in the multimerization of AtTRB1. 相似文献
33.
Tyler J. Slade Trevor P. Bailey Jann A. Grovogui Xia Hua Xiaomi Zhang Jimmy Jiahong Kuo Ido Hadar G. Jeffrey Snyder Chris Wolverton Vinayak P. Dravid Ctirad Uher Mercouri G. Kanatzidis 《Liver Transplantation》2019,9(30)
PbSe is an attractive thermoelectric material due to its favorable electronic structure, high melting point, and lower cost compared to PbTe. Herein, the hitherto unexplored alloys of PbSe with NaSbSe2 (NaPbmSbSem+2) are described and the most promising p‐type PbSe‐based thermoelectrics are found among them. Surprisingly, it is observed that below 500 K, NaPbmSbSem+2 exhibits unorthodox semiconducting‐like electrical conductivity, despite possessing degenerate carrier densities of ≈1020 cm?3. It is shown that the peculiar behavior derives from carrier scattering by the grain boundaries. It is further demonstrated that the high solubility of NaSbSe2 in PbSe augments both the thermoelectric properties while maintaining a rock salt structure. Namely, density functional theory calculations and photoemission spectroscopy demonstrate that introduction of NaSbSe2 lowers the energy separation between the L‐ and Σ‐valence bands and enhances the power factors under 700 K. The crystallographic disorder of Na+, Pb2+, and Sb3+ moreover provides exceptionally strong point defect phonon scattering yielding low lattice thermal conductivities of 1–0.55 W m‐1 K‐1 between 400 and 873 K without nanostructures. As a consequence, NaPb10SbSe12 achieves maximum ZT ≈1.4 near 900 K when optimally doped. More importantly, NaPb10SbSe12 maintains high ZT across a broad temperature range, giving an estimated record ZTavg of ≈0.64 between 400 and 873 K, a significant improvement over existing p‐type PbSe thermoelectrics. 相似文献
34.
Mechanically Robust BiSbTe Alloys with Superior Thermoelectric Performance: A Case Study of Stable Hierarchical Nanostructured Thermoelectric Materials 下载免费PDF全文
Yun Zheng Qiang Zhang Xianli Su Hongyao Xie Shengcheng Shu Tianle Chen Yonggao Yan Xinfeng Tang Ctirad Uher G. Jeffrey Snyder 《Liver Transplantation》2015,5(5)
Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma‐activated sintering (MS‐PAS) method is employed for commercial p‐type zone‐melted (ZM) ingots of Bi0.5Sb1.5Te3. This fast synthesis approach achieves hierarchical structures and in‐situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS‐PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS‐PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS‐PAS synthesized samples, the MS‐PAS technique demonstrates great potential for mass production and large‐scale applications of Bi2Te3 related thermoelectrics. 相似文献
35.
Engineering Temperature‐Dependent Carrier Concentration in Bulk Composite Materials via Temperature‐Dependent Fermi Level Offset 下载免费PDF全文
Si Hui Wenpei Gao Xu Lu Anurag Panda Trevor P. Bailey Alexander A. Page Stephen R. Forrest Donald T. Morelli Xiaoqing Pan Kevin P. Pipe Ctirad Uher 《Liver Transplantation》2018,8(3)
Precise control of carrier concentration in both bulk and thin‐film materials is crucial for many solid‐state devices, including photovoltaic cells, superconductors, and high mobility transistors. For applications that span a wide temperature range (thermoelectric power generation being a prime example) the optimal carrier concentration varies as a function of temperature. This work presents a modified modulation doping method to engineer the temperature dependence of the carrier concentration by incorporating a nanosize secondary phase that controls the temperature‐dependent doping in the bulk matrix. This study demonstrates this technique by de‐doping the heavily defect‐doped degenerate semiconductor GeTe, thereby enhancing its average power factor by 100% at low temperatures, with no deterioration at high temperatures. This can be a general method to improve the average thermoelectric performance of many other materials. 相似文献
36.
Albert Rivas‐Ubach José A. Hódar Jordi Sardans Jennifer E. Kyle Young‐Mo Kim Michal Oravec Otmar Urban Alex Guenther Josep Peñuelas 《Ecology and evolution》2016,6(13):4372-4386
The debate whether the coevolution of plants and insects or macroevolutionary processes (phylogeny) is the main driver determining the arsenal of molecular defensive compounds of plants remains unresolved. Attacks by herbivorous insects affect not only the composition of defensive compounds in plants but also the entire metabolome. Metabolomes are the final products of genotypes and are constrained by macroevolutionary processes, so closely related species should have similar metabolomic compositions and may respond in similar ways to attacks by folivores. We analyzed the elemental compositions and metabolomes of needles from three closely related Pinus species with distant coevolutionary histories with the caterpillar of the processionary moth respond similarly to its attack. All pines had different metabolomes and metabolic responses to herbivorous attack. The metabolomic variation among the species and the responses to folivory reflected their macroevolutionary relationships, with P. pinaster having the most divergent metabolome. The concentrations of terpenes were in the attacked trees supporting the hypothesis that herbivores avoid plant individuals with higher concentrations. Our results suggest that macroevolutionary history plays important roles in the metabolomic responses of these pine species to folivory, but plant–insect coevolution probably constrains those responses. Combinations of different evolutionary factors and trade‐offs are likely responsible for the different responses of each species to folivory, which is not necessarily exclusively linked to plant–insect coevolution. 相似文献
37.
Regina Sepsiova Ivona Necasova Smaranda Willcox Katarina Prochazkova Peter Gorilak Jozef Nosek Ctirad Hofr Jack D. Griffith Lubomir Tomaska 《PloS one》2016,11(4)
Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast. 相似文献
38.
Natural and modified preparations of lipopolysaccharides and lipopolysaccharide-protein complexes isolated from the S- and R-form of Shigella dysenteriae serovar 1 were found to markedly inhibit the initial growth of mouse solid tumors derived from Németh-Kellner lymphoma, Gardner 6C3HED lymphoma, an ill-defined syngeneic lymphoma of DBA mice (Skalsky lymphoma) and LP-2 plasmacytoma. The biopreparations were given intraperitoneally, most frequently at a dose range from 50 to 200 micrograms per mouse; significant inhibitory effects on tumor growth were evidenced even in mice bearing tumors weighing 113 to 507 mg. 相似文献
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