Thermoelectric performance of co-doped SnTe with resonant levels

Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n_H) and extrinsic dopant concentration (N_I, N_(Ag)) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n_H. Upon substituting extrinsic dopants beyond a certain amount, the nH changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials

Optimization of thermoelectric efficiency in SnTe: the case for the light band

p-Type PbTe is an outstanding high temperature thermoelectric material with zT of 2 at high temperatures due to its complex band structure which leads to high valley degeneracy. Lead-free SnTe has a similar electronic band structure, which suggests that it may also be a good thermoelectric material. However, stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1 × 10^(20) cm^(−3), which corresponds to a minimum Seebeck coefficient and zT. While in the case of p-PbTe (and n-type La3Te4) one would normally achieve higher zT by using high carrier density in order to populate the secondary band with higher valley degeneracy, SnTe behaves differently. It has a very light, upper valence band which is shown in this work to provide higher zT than doping towards the heavier second band. Therefore, decreasing the hole concentration to maximize the performance of the light band results in higher zT than doping into the high degeneracy heavy band. Here we tune the electrical transport properties of SnTe by decreasing the carrier concentration with iodine doping, and increasing the carrier concentration with Gd doping or by making the samples Te deficient. A peak zT value of 0.6 at 700 K was obtained for SnTe0.985I0.015 which optimizes the light, upper valence band, which is about 50% higher than the other peak zT value of 0.4 for Gd_zSn_(1−zT)e and SnTe_(1+y) which utilize the high valley degeneracy secondary valence band

Thermoelectric performance of co-doped SnTe with resonant levels

Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n_H) and extrinsic dopant concentration (N_I, N_(Ag)) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n_H. Upon substituting extrinsic dopants beyond a certain amount, the nH changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials

Thermoelectric properties of S and Te-doped Cu2SnSe3 prepared by combustion synthesis

S and Te-doped Cu2SnSe3 samples with chemical formula of Cu2SnSe3-xSx and Cu2SnSe3-xTex (x = 0.05, 0.10, 0.15, 0.20) are prepared, and the effect of S and Te-doping on thermoelectric properties is investigated. In all the samples, the Cu2SnSe3 phase is synthesized as the major product, and its lattice parameters decrease with S-doping but increase with Te-doping. EDS analysis confirms the incorporation of S and Te dopants in the Cu2SnSe3 phase, and reveals an element segregation in the Te-doped samples. S- and Te-doping decreases the electrical conductivity, enhance the Seebeck coefficient, and reduce the thermal conductivity. S-doping is effective to improve the ZT of Cu2SnSe3, and the Cu2SnSe3-xSx sample with x = 0.05 shows a ZT of 0.66 at 773 K, which is improved by more than 50% compared with that of the undoped sample. On the contrary, Te-doping leads to decreased ZT values owing to the significant reduction in electrical conductivity

Geology and Petrogeochemistry of Lijiapuzi Nb-Ta Granitic Pegmatite Deposit: Implications for Ore Genesis and Prospecting

Most of the rare metal pegmatite deposits in China lie in West, Central and South China, and the Lijiapuzi Nb-Ta deposit is the only pegmatite-type Nb-Ta deposit in Northeast China, therefore a detailed study of the Lijiapuzi deposit is of great importance to the metallogeny and exploration of rare metal deposits in Northeast China. The Nb-Ta bearing pegmatites in Lijiapuzi district are composed of a microcline wall zone, a muscovite (lepidolite)-albite intermediate zone and a quartz core, and the rare metal mineralization mainly occurs in the intermediate zone and is intimately related to the albitization. The lithogeochemical features indicate that Lijiapuzi pegmatoids are rich in silicon and alkaline, poor in calcium, magnesium, titanium and phosphorus, and belong to peraluminous granitoid rocks. The enrichment of large ion lithophile elements (LILEs) and depletion of high field-strength elements (HFSEs), the distinct right-inclined REE pattern with obvious Eu negative anomaly, lower ratio of Nb/Ta and higher ratio of La/Nb and Rb/Sr indicate that the pegmatite was of a crustal origin and formed in relatively extensional tectonic setting of post-orogenesis. The pegmatites in Lijiapuzi area can be divided into two categories, i.e., the NW-trending pegmatites are shorter and thicker, with obvious zoning and localized in the upper part of the near-surface, while the NE-trending pegmatites are longer, thinner, devoid of zoning and localized in the lower part of the district. This probably means that excellent ore prospecting potential exists in the lower part of the Lijiapuzi district

Monitoring Strain Response of Epoxy Resin during Curing and Cooling Using an Embedded Strain Gauge

The present work describes the monitoring system of the real-time strain response on the curing process of epoxy resin from the initial point of curing to the end, and the change in strain during temperature changes. A simple mould was designed to embed the strain gauge, thermometer, and quartz standard sample into the epoxy resin, so that the strain and the temperature were simultaneously measured and recorded. A cryogenic-grade epoxy resin was tested and the Differential Scanning Calorimetry (DSC) was used to analyse the curing process. Based on the DSC results, three curing processes were adopted to investigate their influence on strain response as well as residual strain of the epoxy resin. Moreover, impact strength of the epoxy resin with various curing temperatures were tested and the results indicate that the curing plays a crucial role on the mechanical properties. The method will find cryogenic application of epoxy adhesives and epoxy resin based composites to monitor the strain during the curing process as well as the cryogenic service

Histone demethylase KDM1A promotes hepatic steatosis and inflammation by increasing chromatin accessibility in NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease without specific Food and Drug Administration-approved drugs. Recent advances suggest that chromatin remodeling and epigenetic alteration contribute to the development of NAFLD. The functions of the corresponding molecular modulator in NAFLD, however, are still elusive. KDM1A, commonly known as lysine-specific histone demethylase 1, has been reported to increase glucose uptake in hepatocellular carcinoma. In addition, a recent study suggests that inhibition of KDM1A reduces lipid accumulation in primary brown adipocytes. We here investigated the role of KDM1A, one of the most important histone demethylases, in NAFLD. In this study, we observed a significant upregulation of KDM1A in NAFLD mice, monkeys, and humans compared to the control group. Based on these results, we further found that the KDM1A can exacerbate lipid accumulation and inflammation in hepatocytes and mice. Mechanistically, KDM1A exerted its effects by elevating chromatin accessibility, subsequently promoting the development of NAFLD. Furthermore, the mutation of KDM1A blunted its capability to promote the development of NAFLD. In summary, our study discovered that KDM1A exacerbates hepatic steatosis and inflammation in NAFLD via increasing chromatin accessibility, further indicating the importance of harnessing chromatin remodeling and epigenetic alteration in combating NAFLD. KDM1A might be considered as a potential therapeutic target in this regard