Type Bi Research Articles

Improved Thermoelectric Performance in n–type Bi2(Te,Se)3 Alloys through the Incorporation of Fe Nanoparticles

Improved Thermoelectric Performance in n–type Bi₂(Te,Se)₃ Alloys through the Incorporation of Fe Nanoparticles

Analysis of Thermoelectric Properties of Hot-deformed Bismuth Telluride Sintered Materials

Bismuth telluride (Bi2Te3)-based alloys are widely used for thermoelectric cooling and power generation at low temperatures, and they are the only commercially available materials for thermoelectric applications below 500 K. The rhombohedral unit cell with a large c/a lattice constant ratio consisting of - Te-Bi-Te-Bi-Te- stacked layers inevitably brings about a large anisotropy in transport properties, which is why texturing is very important in polycrystalline Bi2Te3</sub alloys for maximum performance. In this report, p and n-type polycrystalline Bi2Te3</sub alloys were synthesized and hot-deformed to investigate the effects of texturing on thermoelectric properties. Hot deformation (HD) induces the strong alignment of (001) orientations along the compression direction, and a remarkable increase in the orientation factor F of (001) orientations is observed after HD in both p and n-type materials. All of the hot-deformed polycrystalline samples showed increased electrical conductivity (σ), power factor (PF), and thermal conductivity (k) in the in-plane (IP) direction, and vice versa in the out-of-plane (OOP) direction, which makes the IP direction of the hot-deformed bodies more favorable for module fabrication in terms of power factor, for both p and n-type Bi2Te3</sub-based alloys. However, due to the different degree of anisotropy of k and σ, the figures of merit (zT) were maximized in the OOP direction in the p-type materials after HD, whereas the zTs of the n-type materials were higher in the IP direction. This occurs because the anisotropy factor of electron conduction is higher than that of hole conduction, which more than offsets the advantage of the smaller k in the c-direction of n-type Bi2Te3</sub. The maximum zT of 1.33 (OOP) and 0.90 (IP) were obtained after HD from the p and n-type Bi2Te3 alloys, respectively, which were 9.3% and 18.4% higher than those of as-sintered materials.

Occurrence of Hysterothylacium Species (Nematoda: Raphidascarididae) from Some Marine Fishes from Iraqi Waters

Parasitological investigation of 22 species of marine fishes in territorial Iraqi waters, during the period from October 2019 till September 2020, revealed recording of six different species of Hysterothylacium Ward & Magath, 1917 in different developmental stages. These nematodes including two species in adult stage of Hysterothylacium viz, H. reliquens (Norris & Overstreet, 1975) and Hysterothylacium sp. (females only), two species of fourth larval stages (Hysterothylacium sp. type BH and Hysterothylacium sp. type BI) and two species of third larval stages (Hysterothylacium sp. type BA and Hysterothylacium sp. type BC). Identification of Hysterothylacium sp. was based on female only isolated from Blackfin stonefish Pseudosynanceia melanostigma Day, 1875; Hysterothylacium sp. type BH 4th larval stage isolated from Arabian backspot threadfin Polydactylus mullani (Hora, 1926) and Hysterothylacium sp. type BI 4th larval stage from purple-spotted bigeye Priacanthus tayenus Richardson, 1846; all these parasitic nematodes recorded for the first time in the Arabian Gulf. In addition, 14 fish species are considered as new hosts for Hysterothylacium sp. type BC 3rd larval stage. Description of female Hysterothylacium sp., Hysterothylacium sp. type BH and BI both 4th larval stages are given. The interest record of inverse intestinal caecum in some specimens of 3rd larval stage of Hysterothylacium type BC in some marine fishes of the current study is given.

CHARACTERIZATION OF BI-NULL SLANT(BNS) HELICES OF (k,m )-TYPE IN R^3_1 AND R^5_ 2

The present study discusses bi-null slant helices of $(k, m)$ type in $R_2^5$ and give the characterization for a curve to be certain $(k,m)$ type bi null slant helix (BNS helix). The discussion includes the proofs for the non existence cases of $(k,m)$ type bi null slant helices in $R_2^5$. Moreover certain characterizations and non existence have also been obtained for bi null slant helix to be $(k,m)$ type using modified orthogonal frame.

Overexpression of NgBR inhibits high-fat diet-induced atherosclerosis in ApoE-deficiency mice.

Hyperlipidemia (hypercholesterolemia and/or hypertriglyceridemia) is a risk factor for atherosclerosis. Nogo-B receptor (NgBR) plays important roles in hepatic steatosis and cholesterol transport. However, the effect of NgBR overexpression on atherosclerosis remains unknown. Apolipoprotein E deficient (ApoE-/-) mice infected with adeno-associated virus (AAV)-NgBR expression vector were fed a high-fat diet for 12 weeks, followed by determination of atherosclerosis and the involved mechanisms. We determined that high expression of NgBR by AAV injection mainly occurs in the liver and it can substantially inhibit en face and aortic root sinus lesions. NgBR overexpression also reduced levels of inflammatory factors in the aortic root and serum, and levels of cholesterol, triglyceride, and free fatty acids in the liver and serum. Mechanistically, NgBR overexpression increased the expression of scavenger receptor type BI and the genes for bile acid synthesis, and decreased the expression of cholesterol synthesis genes by reducing sterol regulatory element-binding protein 2 maturation in the liver, thereby reducing hypercholesterolemia. In addition, NgBR overexpression activated AMP-activated protein kinase α via the Ca2+ signaling pathway, which inhibited fat synthesis and improved hypertriglyceridemia. Taken together, our study demonstrates that overexpression of NgBR enhanced cholesterol metabolism and inhibited cholesterol/fatty acid synthesis to reduce hyperlipidemia, and reduced vascular inflammation, thereby inhibiting atherosclerosis in ApoE-/- mice. Our study indicates that NgBR might be a potential target for atherosclerosis treatment.

Electronic Transport Properties of Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> Fabricated by Hot Extrusion

Herein we report the optimized processing conditions of hot extrusion for fabricating an <i>n</i>-type Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> thermoelectric compound, with high electronic transport properties as well as improved mechanical reliability. We fabricated a Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> extrudate that was 3.8 mm in diameter and 700 mm in length by controlling the processing parameters of temperature and pressure. A 3-point bending strength of over 70 MPa, which is 7 times higher that of the commercial zone melting ingot, was obtained in the samples prepared at 460 <sup>o</sup>C temperature under 6–6.5 MPa pressure. The samples benefitted from the formation of a highly-dense microstructure (relative density > 98%). It is noted that the electronic transport properties (electrical conductivity and Seebeck coefficient) could be manipulated by controlling the applied pressure of hot extrusion at 460 <sup>o</sup>C, mainly due to the change in the characteristics of the 00<i>l</i> crystal orientation, which originated from grain rotation and rearrangement. Power factor values of ~2.9 mW/mK<sup>2</sup> at 300 K and ~2.95 mW/mK<sup>2</sup> at 320 K, similar to those of sintered bulks, were obtained in the hot extrudate fabricated under processing parameters of 460 <sup>o</sup>C and 6 MPa. Moreover, a high power factor value of 2.25 mW/mK<sup>2</sup> was observed even at the high temperature of 480 K, which is 70% higher than that of Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> bulk fabricated by hot pressing.

Inhibiting the bipolar effect via band gap engineering to improve the thermoelectric performance in n-type Bi2-Sb Te3 for solid-state refrigeration

• Se replacement can enlarge the E g and thus effectively mitigate the bipolar effect. • The manipulation of donor-like effect retains the optimized carrier concentration. • The large strain field and mass fluctuation reduce lattice thermal conductivity. • A state-of-the-art zT = 1.0 at 300 K is attained for n -type Bi 1.5 Sb 0.5 Te 2.8 Se 0.2 . • n -type Bi 2- x Sb x Te 3 becomes a promising candidate for solid-state cooling field. To date, the benchmark Bi 2 Te 3 -based alloys are still the only commercial material system used for thermoelectric solid-state refrigeration. Nonetheless, the conspicuous performance imbalance between the p -type Bi 2- x Sb x Te 3 and n -type Bi 2 Te 3- x Se x legs has become a major obstacle for the improvement of cooling devices to achieve higher efficiency. In our previous study, novel n -type Bi 2- x Sb x Te 3 alloy has been proposed via manipulating donor-like effect as an alternative to mainstream n -type Bi 2 Te 3- x Se x . However, the narrow bandgap of Bi 2- x Sb x Te 3 provoked severe bipolar effect that constrained the further improvement of zT near room temperature. Herein, we have implemented band gap engineering in n -type Bi 1.5 Sb 0.5 Te 3 by employing isovalent Se substitution to inhibit the undesired intrinsic excitation and achieve the distinguished room-temperature zT . First, the preferential occupancy of Se at Te 2 site appropriately enlarges the band gap, thereby concurrently improving the Seebeck coefficient and depressing the bipolar thermal conductivity. In addition, the Se alloying mildly suppresses the compensation mechanism and essentially preserves the already optimized carrier concentration, which maintains the peak zT near room temperature. Moreover, the large strain field and mass fluctuation generated by Se alloying leads to the remarkable reduction of lattice thermal conductivity. Accordingly, the zT value of Bi 1.5 Sb 0.5 Te 2.8 Se 0.2 reaches 1.0 at 300 K and peaks 1.1 at 360 K, which surpasses that of most well-known room-temperature n -type thermoelectric materials. These results pave the way for n -type Bi 2- x Sb x Te 3 alloys to become a new and promising top candidate for large-scale solid-state cooling applications.

Mid-cretaceous rapid denudation of Eastern Tibetan plateau: Insights from detrital records at the Southwestern corner of Sichuan basin

Reconstruction of the Cretaceous tectonic evolution of the eastern margin of the Tibetan Plateau is of great significance to understanding the formation and early evolution of the Tibetan Plateau. The thick late Mesozoic sedimentary sequence in the Western Sichuan Basin may record the evolution of the basin itself and the tectonic uplift history of the eastern margin of the Tibetan Plateau during the Cretaceous period. Here we provide new multi-proxy provenance data from conglomerate clast populations, sandstone petrography, heavy mineral assemblages, U-Pb dating of detrital zircon, paleocurrent data, and detrital garnet geochemistry from the Cretaceous clastic units in the southwest corner of Sichuan Basin. Our analysis reveals two distinct changes in sediment provenance recorded in the Cretaceous strata at the southwest corner of the Sichuan Basin. The first significant change of detrital provenance was identified in the mid-Cretaceous Jiaguan Formation. Metamorphic rocks and volcanic rocks clast, as well as feldspar and mica, increased significantly, a heavy mineral assemblage dominated by hematite–limonite and ilmenite with high ATi and RuZi and low ZTR values, predominantly type Bi garnet and mostly 164 Ma, 207 Ma, 440 Ma, 780 Ma–824 Ma, and 1840 Ma detrital zircon ages, interpreted to be sourced from the Songpan-Ganzi fold belt and Longmenshan orogenic belt. The second shift, in the Guankou Formation, is marked by a low compositional maturity, a distinct increase in fossiliferous carbonate clasts and high GZi index with type Bii garnet, and Triassic zircon ages, indicating the exhumation of Longmenshan orogenic belt during the late Cretaceous. These data collectively indicate that the significant surface uplift and rapid denudation of the eastern margin of the Tibetan Plateau were probably initiated in the mid-Cretaceous (∼120 Ma). In conclusion, a detailed hands-on provenance analysis of the clastic sedimentary sequences in the southwest corner of the Sichuan Basin enabled us to determine catchment areas and shifts hitherto unstudied, thus contributing to the exhumation history of the eastern margin of the Tibetan Plateau.

To Use an Ant Colony Technique to Solve a Crispy Type Bi- and Tri-Objective Transportation Problem

Transportation problem (TP) aims to reduce the entire transportation cost of moving resources from various supply hubs to various demand hubs. However, in real-life situations, all organizations want to achieve numerous objectives while making transportation of goods. The degree of deterioration may vary depending on the mode, route, and time of transport. In some cases, the multiobjective could be used to reduce the use of a scarce resource, such as energy. As a result, the proposed approach was discovered to be an algorithm that improves bi- and triobjective TP techniques. This is an innovative way for solving the new bi- and triobjective transportation algorithm using a modified ant colony optimization (ACO) algorithm. According to the literature, various strategies have been developed in the past to tackle the multiobjective transportation problem (MOTP). The MOTP is solved using goal programming, fuzzy programming, interactive solution algorithms, and other techniques. These strategies are occasionally good or bad in achieving better results in a reasonable amount of time. The heuristic technique used in this work is the improved ACO algorithm, which is based on the ant colony algorithm and has been found to provide solutions with a reasonable degree of satisfaction for two and three objective TPs. When the findings are compared, the solution achieved using the proposed method has delivered the best performance and provides a case study to show the new strategy.

Impact of Lynch syndrome, BRAFV600E, and RAS mutations on outcomes in MSI/dMMR metastatic colorectal cancer (mCRC) treated with immune checkpoint inhibitors (ICI): Analysis of combined international cohorts.

171 Background: ICI have demonstrated efficacy in patients (pts) with MSI/dMMR mCRC . Lynch (LS) vs sporadic (Sp) status, BRAFV600E and RAS mutations (mt) are known factors of clinical and molecular heterogeneity in this population. We aimed to evaluate the prognostic value of these parameters in ICI-treated MSI mCRC pts. Methods: Pts are drawn from international cohorts (France, Italy, Spain, and USA). Pts were considered to have cancer linked to LS only in case of determined germline mutation and Sp in case of loss of MLH1/PMS2 protein expression associated with BRAF V600E mutation and/or hypermethylation of MLH1 promoter, or in case of biallelic somatic mutations of MMR genes. Survival analyses: progression-free survival (PFS) per iRECIST criteria and overall survival (OS) were adjusted on prognostic modifiers, selected on unadjusted analysis (p < 0.2) in case of limited number of events. Results: On the 466 pts included, 112 (24%) received ICI in first line, 305 (65%) received anti-PD1 alone, 161 (35%) anti-PD1 plus anti-CTLA4, 129 (29%) had BRAFV600Emt and 153 (34%) RASmt. Median follow-up was 24.0 months. In adjusted analysis of the whole population (n=466; 186 PFS events and 143 OS events), no association with PFS and OS was observed for BRAFV600E mt (PFS HR 1.20 [0.80 to 1.79], p=0.372; OS HR 1.06 [0.66 to 1.70], p= 0.811) and RASmt (PFS HR 0.93 [0.64 to 1.36], p= 0.712; OS HR 0.75 [0.48 to 1.17] p= 0.202). Adjusting factors were age, ECOG status, number of prior chemotherapies, treatment type (bi vs monotherapy), sidness (right vs left + rectum), primary tumor surgery. Concerning the population with determined Lynch status (n= 242; 83 PFS events and 54 OS events), PFS results are displayed. The analysis of impact of LS was not adjusted on BRAFV600E mutational status due to collinearity. In adjusted analysis, LS improved PFS compared with Sp (HR = 0.49, 95%CI (0.25 to 0.96), p = 0.036). Adjusted HR for OS was 0.56 without reaching significance 95%CI (0.25 to 1.22), p = 0.143. Conclusions: In this analysis of ICI-treated MSI/dMMR mCRC pts, RAS/BRAFV600E mutations are not associated with survival while Lynch syndrome pts demonstrated improved PFS. [Table: see text]

Topological insulator VxBi1.08-Sn0.02Sb0.9Te2S as a promising n-type thermoelectric material

As one of the most important n -type thermoelectric (TE) materials, Bi 2 Te 3 has been studied for decades, with efforts to enhance the thermoelectric performance based on element doping, band engineering, etc. In this study, we report a novel bulk-insulating topological material system as a replacement for n -type Bi 2 Te 3 materials: V doped Bi 1.08 Sn 0.02 Sb 0.9 Te 2 S (V:BSSTS). The V:BSSTS is a bulk insulator with robust metallic topological surface states. Furthermore, the bulk band gap can be tuned by the doping level of V, which is verified by magnetotransport measurements. Large linear magnetoresistance is observed in all samples. Excellent thermoelectric performance is obtained in the V:BSSTS samples, e.g., the highest figure of merit ZT of ~ 0.8 is achieved in the 2% V doped sample (denoted as V 0.02 ) at 530 K. The high thermoelectric performance of V:BSSTS can be attributed to two synergistic effects: (1) the low conductive secondary phases Sb 2 S 3 , and V 2 S 3 are believed to be important scattering centers for phonons, leading to lower lattice thermal conductivity; and (2) the electrical conductivity is increased due to the high-mobility topological surface states at the boundaries. In addition, by replacing one third of costly tellurium with abundant, low-cost, and less-toxic sulfur element, the newly produced BSSTS material is inexpensive but still has comparable TE performance to the traditional Bi 2 Te 3 -based materials, which offers a cheaper plan for the electronics and thermoelectric industries. Our results demonstrate that topological materials with unique band structures can provide a new platform in the search for new high performance TE materials. • The high conductive topological surface state of the V:BSSTS samples is considered to be responsible for the good thermoelectric behavior. • Low thermal conductivity: Sb 2 S 3 and V 2 S 3 secondary phases effectively scatter phonons leading to low lattice thermal conductivity. • High ZT throughout the whole temperature range: a ZT max of ~0.8 is achieved in the 2% V doped sample, and the ZT values keep high through the whole temperature range.

Estimation of spring barley adaptability to the aridity of the Stavropol Territory according to the trait ‘1000-grain weight’

A necessary condition for the stable improvement of barley production in the country is the extension of crops, varieties which are most adapted to the conditions of the region, capable of providing a high and stable level of productivity under changing climatic conditions. Productivity is a complex quantitative indicator, which is formed by various yield structure elements, one of which is ‘1000-grain weight’. The purpose of the current study was to estimate adaptability of the spring barley samples of various geographical origins to the arid conditions of the Stavropol Territory according to the trait ‘1000-grain weight’ and their further use in breeding work. The objects of the study were 60 spring barley samples. In order to determine stability, there has been used a coefficient of variation (V %), ecological adaptability (bi), homeostaticity (Hom), and stress tolerance (Ymin–Ymax). On average, during 2016–2021, the trait ‘1000-grain weight’ among the varieties ranged from 35 to 50 grams. The maximum values of the trait ‘1000-grain weight’ were identified in the varieties ‘Victor’ (Russia) with 50.1g (+5.0% to the standard) and ‘Nutans 74840’ (Russia) with 49.7g (+4.2%). The varieties of the extensive type (bi = 0.49–0.86) ‘Nutans 74840’ (Russia), ‘Prikumsky 22’ (Russia), ‘Pri­kumsky 14’ (Russia) and the standard variety ‘Strannik’ were characterized with high stability (V = 5.9–9.8 %), stress tolerance (Ymin–Ymax= –8–11) and homeostaticity (Hom = 43.1–101.2). The varieties ‘Adapt’ (Ukraine), ‘Vodogray’ (Ukraine) and ‘Novonikolaevsky’ (Russia) responded to the weather improvement to a greater extent (bi = 1.21–1.59), but significantly reduced 1000-grain weight when it worsened (Ymin–Ymax = –17 –21). The varieties ‘Nutans 74840’ and ‘Strannik’ turned to be the most adaptive ones for the aridity of the Stavropol Territory, and therefore the best breeding material.

Enhanced thermoelectric performance of n-type Bi2Te2.7Se0.3 via a simple liquid-assisted shear exfoliation

• By using a simple approach of liquid-assisted shear exfoliation (LASE) coupled with SPS, highly-oriented bulk ceramics of Bi 2 Te 2.7 Se 0.3 with effectively reduced grain size were obtained. • A peak ZT value of 0.83 at 448 K was obtained in-plane due to a synergy of enhanced power factor and suppressed lattice and bipolar thermal conductivities, which is 95% higher that of the pristine sample, demonstrating LASE as a useful assistant process for enhancing the performance of layered thermoelectric materials. A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasma sintering (SPS) was applied for n -type Bi 2 Te 2.7 Se 0.3 and the effects on microstructure and anisotropic transport properties were investigated. Results revealed an effective reduction of average grain size due to LASE and a high texturing in the bulks. Moreover, along the in-plane direction, electrical conductivity was increased noticeably due to an enhanced carrier concentration, leading to a significantly improved power factor of 25 μW cm –1 K –2 at 303 K. Meanwhile, the total thermal conductivity was reduced effectively owing to reduction both in lattice component due to enhanced phonon scattering with the grain size reduction, and in the bipolar component inhibited by the increased carrier concentration. Ultimately, a peak thermoelectric figure of merit (ZT) value of 0.83 was obtained at 448 K along the in-plane direction, increased by 95% compared with the pristine one. These results demonstrate the LASE process as a useful assistant method for enhancing the TE performance of layered materials.

Control of Cu-doping behavior in n-type Cu0.01Bi1.99Te2.7Se0.3 polycrystalline bulk via fabrication technique change

Bi–Te-based alloys are potential candidates for use in thermoelectric (TE) modules for low-mid-temperature energy harvesting. However, n -type Bi–Te–Se alloys are inferior to their p -type counterparts in terms of TE performance. It has been found that doping Cu atoms into n -type Bi–Te–Se alloys is effective in improving the TE properties; however, different studies have reported contrasting roles of Cu dopants in the transport properties of Bi–Te–Se alloys. This is attributed to the complex doping behaviors of Cu atoms. In this study, it is demonstrated that employing an appropriate fabrication technique can enable more Cu dopants to be directed to specific atomic sites than others. As part of the study, two n -type polycrystalline Cu 0.01 Bi 1.99 Te 2.7 Se 0.3 bulk samples are respectively fabricated via melt-spinning followed by spark plasma sintering, and via ball-milling followed by spark plasma sintering. The majority of Cu dopants in the melt-spun sample are suspected to exist in between Te 1 –Te 1 atomic layers (van der Waals gap), given the elongated c -axis, increased Hall carrier concentration, and improved non-degenerate mobility (intercalated Cu generates one electron and acts as an electric connector). Resultantly, a ~30% enhancement in the TE figure-of-merit (~0.92 at 360–400 K) is achieved in the melt-spun sample, relative to the ball-milled sample, wherein Cu atoms substitute Bi atoms.

Effect of Zn on thermoelectric power in superconducting Bi2Sr2CaxZn1−xCu2O8+y compounds

For the first time, studies of the temperature dependences of the thermoelectric power for various compositions of Bi2Sr2CaxZn1−xCu2O8+y (x = 1; 0.8; 0.4) in the range 77–320 K have been carried out. The obtained experimental results are analyzed within the framework of the Xin’s two-band model. The concentration of holes per copper atom and the band gap of the semiconductor type Bi–O layers are determined. It is shown that the replacement of the calcium element with zinc in these proportions does not lead to a change in the electronic band structure of Bi2Sr2CaCu2O8+y.

Thermoelectric and Galvanomagnetic Properties of the Alloy Bi<sub>2</sub>Te<sub>3</sub> + 0.04 Weight% Ni in the Temperature Range 77 ÷ 300 K

The article introduces Hi input to p -type Bi₂Te₃ thermoelectric materials under inert gas pressure and presents the results of the study of electrical conductivity, Hall coefficients, thermoelectric and galvanomagnetic properties in the temperature range 77 ÷ 300K. The study of thermoelectric properties has shown that in order to explain the temperature dependence of the heat transfer parameter and the ratio of thermoelectric power to temperature, it is necessary to take into account the complex structure of the valence zone and the contribution of heavy cavitation in transport. It is shown that in order to explain the temperature dependences of the scattering parameter and the ratio of thermoelectric power to temperature, it is necessary to take into account the complex structure of the valence band and the contribution of heavy holes to transport phenomena. The estimates of the band parameters in the framework of the two-band model give the values of the effective mass of holes on the order of the mass of a free electron and the energy gap between nonequivalent extrema on the order of several hundredths of an eV.

Effects of Adding Transition Metal-Substituted Polyoxotungstates on the Frequency and Temperature-Dependent Dielectric Properties of (Bi1.8Pb0.4)Sr2Ca2Cu3O10+δ Superconducting Phase

In the search for highly responsive dielectric materials, superconducting samples of type (Bi,Pb)-2223 were prepared using the standard solid-state reaction technique, with the addition of three different concentrations of ferrato and mangano-undecatungstosilicate (0.04, 0.12, and 0.20 wt%). The dielectric studies were performed by measuring the parallel capacitance $$C_{p}$$ as well as the dielectric loss factor using LCR HiTESTER. The studies were performed at temperature and frequency ranges starting from room temperature down to 98 K and from 50 kHz up to 5 MHz, respectively. The dielectric behavior was investigated by calculating both dielectric constants ( $$\varepsilon^{\prime}$$ and $$\varepsilon^{\prime\prime}$$ ), loss tangent (Tanδ) and ac conductivity (σac) as a function of frequency, temperature and addition concentrations of the {FeSiW11} and {MnSiW11} polyoxometalates. The results revealed that the dielectric parameters decrease with increasing frequency at each temperature for all the {FeSiW11}x(Bi,Pb)-2223 and {MnSiW11}x(Bi,Pb)-2223 prepared samples. Moreover, $$\varepsilon^{\prime}$$ and σac showed a decreasing trend with an increase in temperature in contrast to the increasing trend shown by $$\varepsilon^{\prime\prime}$$ and Tanδ. Additionally, $$\varepsilon^{\prime\prime}$$ has decreased upon increasing temperature at low frequencies. Accordingly, low {MnSiW11} addition at 0.12 wt% exhibited the highest dielectric constant $$\left( {1.99 \times 10^{7} } \right)$$ and ac conductivity $$61.449$$ (Ω.m)−1 with minimum dissipation (1.078). Furthermore, the ac conductivity was studied according to the power law, and the frequency exponent was found greater than one $$\left( {1.654 \le S \le 1.759} \right)$$ for all the prepared samples.

Материалы на основе твердых растворов теллуридов висмута и сурьмы, полученные методами быстрой кристаллизации расплава

Abstractp -type Bi_0.5Sb_1.5Te_3 solid solutions prepared by hot pressing and the extrusion of powders prepared by rapid melt crystallization methods such as melt spinning and melt crystallization in a liquid are investigated. The morphology of the powders, the sample cleavage surface, and their microstructure are investigated using optical microscopy, scanning electron microscopy, and scanning tunneling microscopy. The mechanical properties of the samples are investigated by room-temperature compression tests. The Seebeck coefficient, electrical conductivity, and thermal conductivity of the materials are measured in the temperature range of 100–600 K. The highest limiting compressive strength σ_B = 145 MPa at 300 K and maximal thermoelectric efficiency ( ZT )_max = 1.34 at 370 K are found for materials extruded from granules prepared by melt crystallization in water and ground in a ball mill.

Материалы на основе твердых растворов халькогенидов висмута n-типа проводимости, полученные кристаллизацией расплава в жидкости

AbstractThe microstructure, mechanical, and thermoelectric properties of samples of the n -type Bi_2Te_3–Bi_2Se_3 solid-solution samples containing 6, 8, and 10 mol % Bi_2Se_3, doped with antimony iodide, cadmium chloride, and hexabromobenzene, are investigated. The samples are formed by hot pressing and the extrusion of granules prepared by melt crystallization in a liquid and ground in a mortar, cutting mill, and ball mill. Measurements are performed at room temperature and in the range of 100–600 K. The formation conditions and compositions of materials with an ultimate compressive strength of ~250 MPa and thermoelectric efficiency of ( ZT )_max = (0.9–1.0) in the temperature range of 320–430 K are found.

Counting Borel Orbits in Symmetric Spaces of Types BI and CII

This is a continuation of our combinatorial program on the enumeration of Borel orbits in symmetric spaces of classical types. Here, we determine the generating series the numbers of Borel orbits in $${\mathbf {SO}}_{2n+1}/{\mathbf {S(O}}_{2p}\times {\mathbf {O}}_{2q+1} \mathbf {)}$$ (type BI) and in $${\mathbf {Sp}}_n/{\mathbf {Sp}}_p \times {\mathbf {Sp}}_q$$ (type CII). In addition, we explore relations to lattice path enumeration.