Hydrothermal Synthesis of Cancrinite from Coal Gangue for the Immobilization of Sr.

The primary objective of this study is to investigate and develop a rapid and effective method for the immobilization of Sr in the event of a nuclear leakage incident. Coal gangue, an underutilized form of solid waste from the coal industry, can be used as a raw material for curing Sr due to its high content of silica-alumina oxides. In the present study, Sr was successfully solidified in cancrinite synthesized using a hydrothermal method with coal gangue as raw material. A stable cancrinite phase was formed at a relative alkali concentration of more than 6 M. When the Sr/Al(Si) ratio was <1/6, cancrinite was the only stable phase that varied with the hydrothermal temperature and time. When the Sr/Al(Si) ratio increased to 1/2, the cancrinite phase completely disappeared, and a new strontium feldspar phase (SrAl2Si2O8) appeared. PCT leaching experiments showed that when Sr/Al(Si) < 1/6, the Sr leaching rate of Sr-cancrinite samples obtained by hydrothermal synthesis at 180 °C for 24 h was very low.

Promoted Na Solubility and Modified Band Structure for Achieving Exceptional Average ZT by Extra Mn Doping in PbTe.

Na doping strategy provides an effective avenue to upgrade the thermoelectric performance of PbTe-based materials by optimizing electrical properties. However, the limited solubility of Na inherently restricts the efficiency of doping, resulting in a relatively low average ZT, which poses challenges for the development and application of subsequent devices. Herein, to address this issue, the introduced spontaneous Pb vacancies and additional Mn doping synergistically promote Na solubility with a further modified valence band structure. Furthermore, the induced massive point defects and multiscale microstructure greatly strengthen the scattering of phonons over a wide frequency range, leading to a remarkable ultralow lattice thermal conductivity of ∼0.42 W m-1 K-1. As a result, benefiting from the significantly enhanced Seebeck coefficient and superior thermal transports, a high peak ZT of ∼2.1 at 773 K and an excellent average ZT of ∼1.4 between 303 and 823 K are simultaneously achieved in Pb0.93Na0.04Mn0.02Te. This work proposes a simple and constructive method to obtain high-performance PbTe-based materials and is promising for the development of thermoelectric power generation devices.

Multifunctional GeMnTe2 Synergistically Optimizes Thermoelectric Properties of SnTe-In2Te3 Alloys.

SnTe-In2Te3 alloys ensure excellent electrical properties in the whole temperature region due to the resonant level. Nevertheless, temperature-sensitive resonance states and single phonon scattering restrict further improvement of thermoelectric performance. Consequently, it is anticipated that additional electrically independent scattering sources should be introduced to impede phonon transport. Here, the SnTe-In2Te3-GeMnTe2 alloy is prepared by further solidifying cubic GeMnTe2, which demonstrates multiple modulation effects. The highly redissolved Mn2+ promotes the valence band convergence, enhances the Seebeck coefficient at higher temperature, and balances the possible weakened resonance level effect at higher carrier concentrations, and a high average power factor (1.94 mW m-1 K-2) is realized over the entire temperature range. Additionally, compensatory vacancies, substitutions, and Ge/Mn precipitates are easily constructed with GeMnTe2 alloying, leading to a further reduction in lattice thermal conductivity, which reaches κl ∼ 0.6 W m-1 K-1 at 850 K. Ultimately, a high peak zT of ∼1.25 (850 K) and a zTave of 0.72 (300-850 K) are realized in (SnTe)2.91(In2Te3)0.03(Ge0.5Mn0.5Te)1.2, and the maximum thermoelectric conversion efficiency of ∼2.8% (ΔT ∼ 450 K) is achieved. The present results indicate multiple effects of GeMnTe2 in enhancing the thermoelectric performance of SnTe-In2Te3 alloys.

Band engineering enhances thermoelectric performance of Ag-doped Sn0.98Se.

Ag doping can effectively increase the carrier concentration ofp-type SnSe polycrystalline, thereby enhancing the thermoelectric (TE) performance. However, the key role of the transport valence band in Ag-doped SnSe remains unclear. Particularly, understanding the influence of evaluating the optimal balance between band convergence and carrier mobility on weighted mobility is a primary consideration in designing high-performance TE materials. Here, we strongly confirm through theoretical and experimental evidence that Ag-doped Sn0.98Se can promote the evolution of valence bands and achieve band convergence and density of states distortion. The significantly increased carrier concentration and effective mass result in a dramatic increase in weighted mobility, which favors the achievement of superior power factors. Furthermore, the Debye model reveals the reasons for the evolution of lattice thermal conductivity. Eventually, a superior average power factor and averagezTvalue are obtained in the Ag-doped samples in both directions over the entire test temperature range. This strategy of improving TE performance through band engineering provides an effective way to advance TEs.

Lead Vacancy Promotes Sodium Solubility to Achieve Ultra-High zT in Only Ternary Pb1- x Nax Te.

Chemical doping of sodium is an indispensable means to optimize thermoelectric properties of PbTe materials, while a bottleneck is that an aliovalent atom doping leads to spontaneous intrinsic defects in the PbTe matrix, resulting in low dopant solubility. Therefore, it is urgent to improve the doping efficiency of Na for maximizing optimization. Here, an amazing new insight that the intentionally introduced Pb vacancies can promote Na solubility in ternary Pb1- x Nax Te is reported. Experimental analysis and theoretical calculations provide new insights into the inherent mechanism of the enhancement of Na solubility. The Pb vacancies and the resultant more dissolved Na not only synergistically optimize the carrier concentration and further facilitate the band convergence, but also induce a large number of dense dislocations in the grains. Consequently, benefiting from the self-enhancement of Seebeck coefficient and the minimization of lattice thermal conductivity, an 18% growth is obtained for the figure of merit zT in vacancy-containing Pb0.95 Na0.04 Te sample, reaching maximum zTmax  ≈ 2.0 at 823 K, which achieves an ultra-high performance in only Na-doped ternary Pb1- x Nax Te materials. The strategy utilized here provides a novel route to optimize PbTe materials and represents an important step forward in manipulating thermoelectrics to improve dopant solubility.

High-Power Factor Enabled by Efficient Manipulation Interaxial Angle for Enhancing Thermoelectrics of GeTe-Cu2Te Alloys.

The emerged strategy of manipulating the rhombohedral crystal structure provides another new degree of freedom for optimizing the thermoelectric properties of GeTe-based compounds. However, the concept is difficult to be effectively measured and often depends on heavy doping that scatters carriers severely. Herein, we synergistically manipulate lattice distortion and vacancy concentration to promote the excellent electrical transport of GeTe-Cu2Te alloys and quantify the interaxial angle-dependent density of state effective mass. Distinct from the conventional electronic coupling effect, about 2% substitution of Zr4+ significantly increases the interaxial angle, thereby enhancing the band convergence effect and improving the Seebeck coefficient. In addition, Ge-compensation attenuates the mobility deterioration, leading to improved power factor over the whole temperature range, especially exceeding ∼22 µW cm-1 K-2 at 300 K. Furthermore, the Debye-Callaway model elucidates low lattice thermal conductivity due to strong phonon scattering from Zr/Ge substitutional defects. As a result, the highest figure of merit zT of ∼1.6 (at 650 K) and average zTave of ∼0.9 (300-750 K) are obtained in (Ge1.01Zr0.02Te)0.985(Cu2Te)0.015. This work demonstrates the effective band modulation of Zr on GeTe-based materials, indicating that the modification of the interaxial angle is a deep pathway to improve thermoelectrics.

Structure Optimization and Multi-frequency Phonon Scattering Boosting Thermoelectrics in Self-Doped CoSb3-Based Skutterudites.

The utilization of thermoelectric devices that directly convert waste heat to electricity is an effective approach to alleviate the global energy crisis. However, the low efficiency of thermoelectric materials has puzzled the widespread applications. The CoSb3-based skutterudites are favored by device integration due to the excellent thermal stability, while the development of pristine CoSb3 materials is limited by the ultra-high thermal conductivity and the poor Seebeck coefficient. In this work, we demonstrate that both structural improvement and strong phonon interaction are realized simultaneously in In-filled CoSb3 coordinated with excessive Sb. The extra Sb compensates the deficiency on the Sb4 ring, improving the Seebeck coefficient, and cooperates with In to further advance the carrier concentration. Therefore, the structure optimization and chemical potential regulation maximize the electrical properties. Thermally, the residual InSb nanoparticles and partial In/Sb-alloying, along with vibration of In in voids, jointly shorten the multi-frequency phonon relaxation time, leading to a dramatic decline in the lattice thermal conductivity. As a result, a maximum zTmax of ∼1.27 at 650 K and an average zTavg of ∼0.9 from 300 to 750 K was obtained in In1.4Co4Sb12 + 8%Sb, respectively. Our findings provide valuable guidance for the selection of CoSb3-based skutterudite dopants to achieve high-performance thermoelectric materials.

Comprehensive Insight into p-Type Bi2Te3-Based Thermoelectrics near Room Temperature.

Bi2Te3 is a well-recognized material for its unique properties in diverse thermoelectric applications near room temperature. The considerable efforts on Bi2Te3-based alloys have been extremely extensive in recent years, and thus the latest breakthroughs in high-performance p-type (Bi, Sb)2Te3 alloys are comprehensively reviewed to further implement applications. Effective strategies to further improve the thermoelectric performance are summarized from the perspective of enhancing the power factor and minimizing the lattice thermal conductivity. Furthermore, the surface states of topological insulators are investigated to provide a possibility of advancing (Bi, Sb)2Te3 thermoelectrics. Finally, future challenges and outlooks are overviewed. This review will provide potential guidance toward designing and developing high-efficient Bi2Te3-based and other thermoelectrics.

Cu2Te Incorporation-Induced High Average Thermoelectric Performance in p-Type Bi2Te3 Alloys.

p-Type (Bi, Sb)2Te3 alloys are attractive materials for near-room-temperature thermoelectric applications due to their high atomic masses and large spin-orbit interactions. However, their narrow band gaps originating from spin-orbit interactions lead to bipolar excitation, thereby limiting average thermoelectrics within a local temperature region (300-400 K). Here, we introduce Cu2Te into the Bi0.3Sb1.7Te3 (BST) lattice to implement high thermoelectrics over a wide temperature range. The carrier concentration is synergistically modulated via Cu substitution and the evolution of intrinsic point defects (antisites and vacancies). Furthermore, the chain effect caused by Cu2Te incorporation in BST is reflected in the improvement of the weighted mobility µW, thereby enhancing the power factor in the whole temperature range. Extrinsic and intrinsic defects due to the incorporation of Cu2Te lead to a significant reduction in the lattice thermal conductivity κL, which is further demonstrated by Raman spectroscopy. Combining κL and µW, the quantity factor B increases from 0.5 to 1 with increasing Cu2Te content due to not only the reduction of κL but also a significant improvement in electrical properties. Eventually, a peak figure of merit (zT) of ∼1.15 at 423 K is achieved in BST-Cu2Te samples, and an average figure of merit (zTave) of ∼1.12 (350-500 K) surpasses other excellent p-type Bi2Te3-based thermoelectrics. Such a synergistic effect can facilitate near-room-temperature thermoelectric applications of Bi2Te3-based alloys and provide chances for the technology space in thermoelectrics.

Honokiol improves depression-like behaviors in rats by HIF-1α- VEGF signaling pathway activation.

Increasing evidence indicates that the pathogenesis of depression is closely linked to impairments in neuronal synaptic plasticity. Honokiol, a biologically active substance extracted from Magnolia Officinalis, has been proven to exert significant antidepressant effects. However, the specific mechanism of action remains unclear. In this study, PC12 cells and chronic unpredictable mild stress (CUMS) model rats were used to explore the antidepressant effects and potential mechanisms of honokiol in vitro and in rats. In vitro experiment, a cell viability detection kit was used to screen the concentration and time of honokiol administration. PC12 cells were administered with hypoxia-inducible factor-1α (HIF-1α) blocker, 2-methoxyestradiol (2-ME), and vascular endothelial growth factor receptor 2 (VEGFR-2) blocker, SU5416, to detect the expression of HIF-1α, VEGF, synaptic protein 1 (SYN 1), and postsynaptic density protein 95 (PSD 95) by western blotting. In effect, we investigated whether the synaptic plasticity action of honokiol was dependent on the HIF-1α-VEGF pathway. In vivo, behavioral tests were used to evaluate the reproducibility of the CUMS depression model and depression-like behaviors. Molecular biology techniques were used to examine mRNA and protein expression of the HIF-1α-VEGF signaling pathway and synaptic plasticity-related regulators. Additionally, molecular docking techniques were used to study the interaction between honokiol and target proteins, and predict their binding patterns and affinities. Experimental results showed that honokiol significantly reversed CUMS-induced depression-like behaviors. Mechanically, honokiol exerted a significant antidepressant effect by enhancing synaptic plasticity. At the molecular level, honokiol can activate the HIF-1α-VEGF signaling pathway in vitro and in vivo, as well as promote the protein expression levels of SYN 1 and PSD 95. Taken together, the results do not only provide an experimental basis for honokiol in the clinical treatment of depression but also suggest that the HIF-1α-VEGF pathway may be a potential target for the treatment of depression.

Antidepressant-Like Effect and Mechanism of Ginsenoside Rd on Rodent Models of Depression.

Background: There is growing evidence to suggest that ginsenoside Rd (GRd) has a therapeutic effect on depression, but the specific mechanisms behind its activity require further study. Objective: This study is designed to investigate the antidepressant-like effect and underlying mechanisms of GRd. Methods: In this study, the behavioral despair mouse model of depression and chronic unpredictable mild stress (CUMS) rat model of depression were established to explore the effects of GRd on depression-like behavior and its underlying mechanisms. Behavioral tests were used to evaluate the replication of animal models and depression-like behaviors. The hypoxia-inducible factor-1α (HIF-1α) blocker 2-methoxyestradiol (2-ME) was injected to determine the role of HIF-1α in the antidepressant-like effect of GRd. In addition, molecular biology techniques were used to determine the mRNA and protein expression of HIF-1ɑ signaling pathway and synaptic plasticity-related regulators, that is synapsin 1 (SYN 1) and postsynaptic density protein 95 (PSD 95). In silico binding interaction studies of GRd with focused target proteins were performed using molecular docking to predict the affinity and optimal binding mode between ligands and receptors. Results: Our data show that GRd significantly reversed depression-like behavior and promoted mRNA and protein expression of HIF-1ɑ signaling pathway and synaptic plasticity-related regulators. However, the antidepressant-like effect of GRd disappeared upon inhibition of HIF-1α expression following administration of 2-ME. Furthermore, molecular docking results showed that GRd possessed significant binding affinity for HIF-1α, VEGF, and VEGFR-2. Conclusion: Our results show that GRd exhibits significant antidepressant-like effect and that HIF-1α signaling pathway is a promising target for the treatment of depression.

Mechanism of Aconiti Kusnezoffii Radix Processed with Chebulae Fructus Against H9c2 Cardiomyocyte Toxicity Based on TRPV1 Channel / 中国实验方剂学杂志

ObjectiveTo explore the role of transient receptor potential vanilloid 1 （TRPV1） channel in reducing cardiomyocyte toxicity of Aconiti Kusnezoffii Radix processed with Chebulae Fructus. MethodH9c2 cardiomyocytes cultured in vitro were used as a model to assess cell viability by methyl thiazolyl tetrazolium （MTT） assay， the expression of TRPV1 mRNA was detected by real-time fluorescence quantitative polymerase chain reaction （Real-time PCR）， and the leakage rate of lactate dehydrogenase （LDH）， the changes of nucleus， reactive oxygen species （ROS）， mitochondrial membrane potential and Ca2+ contents were detected by enzyme linked immunosorbent assay （ELISA）. ResultCompared with the blank group， when the concentration was ≥0.5 g·L-1， the cell viability was significantly decreased （P<0.01）， the leakage rate of LDH， the release of ROS and Ca2+ were increased， the mitochondrial membrane potential was decreased， and the nucleus was pyknosis or even broken in raw Aconiti Kusnezoffii Radix and Aconiti Kusnezoffii Radix processed with Chebulae Fructus groups. When the concentration was ≥0.5 g·L-1， compared with the same mass concentration of raw Aconiti Kusnezoffii Radix group， the cell viability increased significantly （P<0.01）， the leakage rate of LDH， the release of ROS and Ca2+ decreased， the mitochondrial membrane potential increased， and the nuclear morphology improved in Aconiti Kusnezoffii Radix processed with Chebulae Fructus group. Application of the same mass concentration of raw Aconiti Kusnezoffii Radix to H9c2 cardiomyocytes pretreated with the TRPV1 inhibitor BCTC significantly increased cell viability， decreased leakage rate of LDH， ROS and Ca2+ release， increased mitochondrial membrane potential and improved nuclear pyknosis compared with untreated H9c2 cardiomyocytes. Application of the same mass concentration of Aconiti Kusnezoffii Radix processed with Chebulae Fructus to H9c2 cardiomyocytes pretreated with BCTC decreased cell viability， increased LDH leakage rate， ROS and Ca2+ release， reduced mitochondrial membrane potential compared with untreated H9c2 cardiomyocytes. Real-time PCR results showed that both raw Aconiti Kusnezoffii Radix and Chebulae Fructus decoction could increase the expression of TRPV1 mRNA in cardiomyocytes in a concentration dependent manner. ConclusionRaw Aconiti Kusnezoffii Radix can induce cardiomyocyte apoptosis and cardiotoxicity by activating TRPV1 channel， while Aconiti Kusnezoffii Radix processed with Chebulae Fructus can attenuate the toxicity through TRPV1 channel， which may be related to the synergistic effect of acid components in Chebulae Fructus and alkaloids in Aconiti Kusnezoffii Radix on TRPV1 channel.

Isotropic Thermoelectric Performance of Layer-Structured n-Type Bi2Te2.7Se0.3 by Cu Doping.

The lamellar structure of (Bi,Sb)2(Te,Se)3 alloys makes it difficult to achieve isotropic thermoelectric properties in the directions along and perpendicular to the c-axis, especially for n-type samples. In this work, by introducing Cu in polycrystalline n-type CuxBi2Te2.7Se0.3 and applying the traditional synthesis process of high-energy ball milling and hot pressing, substantial enhancement of the thermoelectric figure of merit zT is obtained in both in-plane and out-of-plane directions. The intercalated Cu not only provides electron transport media for mobility improvement but also reduces the lattice thermal conductivity owing to the strain fluctuation. Typically, the van der Waals gap in the out-of-plane direction leads to relatively slower mobility and lower lattice thermal conductivity. Taking into account the same average density-of-state effective mass (mavg* ∼ 1.5me) predicted based on a single parabolic model, the obtained quality factor ß is comparable in both directions. As a result, a peak zT ∼ 1.05 at 420 K and the average zT approaching to 1.0 in the temperature range 300-500 K are obtained in both directions for the Cu0. 02Bi2Te2.7Se0.3 sample. The simple synthesis process and isotropic thermoelectric properties in this work make n-type Bi2Te3 more convenient for potential production and application.

Enhancing Thermoelectrics for Small-Bandwidth n-Type PbTe-MnTe Alloys via Balancing Compromise.

Small-bandwidth n-type PbTe-MnTe alloys effectively modify the valley shape, while it also inevitably aggravates the deterioration of carrier mobility as nonpolar phonons dominate the scattering. It is found that a trace amount of Cu doping can alleviate the compromises among thermoelectric parameters, thereby significantly optimizing the electrical-transport performance near room temperature of n-type PbTe-MnTe alloys. The single-Kane model reveals that the physical origin of performance improvement lies in the carrier mobility enhancement and self-optimization of carrier concentration. The Debye-Callaway model further quantifies the contribution of copper defect scattering to the lattice thermal conductivity. Notably, the high thermoelectric quality factor obtained in this work rationalizes their superior properties and reveals immense potential for achieving higher zT. Herein, an extremely high zT of ∼0.52 at room temperature and a maximum zTmax of ∼1.2 at 823 K are achieved in 0.3% Cu-intercalated n-type PbTe-MnTe. The mechanism in balancing compromise elaborated in principle contributes to an improvement of thermoelectric properties of the n-type PbTe alloys in a broad temperature range.

Enhancing Near-Room-Temperature GeTe Thermoelectrics through In/Pb Co-doping.

The traditional thermoelectric material GeTe has drawn much attention recently because of the reported high thermoelectric performance of the rhombohedral phase in low-temperature ranges, where the split L and Σ band can be reconverged to have a small energy offset and thus high density of state effective mass according to the rhombohedral angle. In addition, In doping in GeTe is also reported to enhance the density of effective mass and therefore increase the Seebeck coefficient because of the induced resonant levels. In this work, In and Pb are doped in GeTe, and In doping leads to an increase in the rhombohedral angle and thus enhanced density of state effective mass in addition to the resonant effect. However, the improved Seebeck coefficient result from In doping is compensated for by a sharp reduction of Hall mobility, leading to no significant enhancement of electronic performance in the rhombohedral phase. By further Pb/Ge doping in the matrix Ge0.95In0.05Te for the optimization of carrier concentration and reduction of lattice thermal conductivity (as low as 0.7 W/mK), a zT as high as ∼1.2 at 550 K and average zT of ∼0.75 between 300 and 550 K are realized in this work, demonstrating GeTe as a promising candidate for near-room-temperature application.

Structural Evolution of High-Performance Mn-Alloyed Thermoelectric Materials: A Case Study of SnTe.

Mn alloying in thermoelectrics is a long-standing strategy for enhancing their figure-of-merit through optimizing electronic transport properties by band convergence, valley perturbation, or spin-orbital coupling. By contrast, mechanisms by which Mn contributes to suppressing thermal transports, namely thermal conductivity, is still ambiguous. A few precedent studies indicate that Mn introduces a series of hierarchical defects from the nano- to meso-scale, leading to effective phonon scattering scoping a wide frequency spectrum. Due to insufficient insights at the atomic level, the theory remains as phenomenological and cannot be used to quantitatively predict the thermal conductivity of Mn-alloyed thermoelectrics. Herein, by choosing the SnTe as a case study, aberration-corrected transmission electron microscopy (TEM)/scanning transmission electron microscopy (STEM) to characterize the lattice complexity of Sn1.02- x Mnx Te is employed. Mn as a "dynamic" dopant that plays an important role in SnTe with respect to different alloying levels or post treatments is revealed. The results indicate that Mn precipitates at x = 0.08 prior to reaching solubility (≈10 mol%), and then splits into MnSn substitution and γ-MnTe hetero-phases via mechanical alloying. Understanding such unique crystallography evolution, combined with a modified Debye-Callaway model, is critical in explaining the decreased thermal conductivity of Sn1.02- x Mnx Te with rational phonon scattering pathways, which should be applicable for other thermoelectric systems.

Coarse-Grained Molecular Dynamics of Protein-lipid Interaction between CD3ε and PIP2 in Lipid Raft Nanodomains / 中国生物化学与分子生物学报

Lipid raft nanodomains of plasma membrane are rich in saturated lipids‚ cholesterol‚ sphingolipids‚ functioning as multimolecular platforms to recruit signaling and trafficking proteins involved in an array of physiological processes‚ which are critical for regulating signal transduction in cell. The staggering complexity of cell membranes and the transient formation of nanodomains greatly hinder research on lipid rafts by traditional experimental means. Molecular dynamics simulations have provided important insight into the organizational principles of cell membranes recently. Simulated membrane systems are under a transition from simple membrane models to multicomponent systems‚ culminating in realistic models of various cell types. Coarse-grained models have been extensively adopted as a powerful tool to explore membrane organization and interactions between lipids and proteins‚ providing efficient computational speed and enabling complex systems. In this work‚ coarse-grained molecular dynamics simulations with MARTINI force field were performed to build a raft-forming membrane with mixed lipids‚ including negatively charged lipid PIP2. Mixed lipids in this model were spontaneously partitioned into binary-phase membrane during 5 μs simulations by low temperature (295 K) treatment‚ forming lipid ordered (Lo) and liquid-disordered (Ld) nanodomains. Results of membrane thickness‚ lipid distribution‚ membrane fluidity‚ order parameters of the acyl tails‚ radial distribution functions were consistent with simulation and experimental data. Addition of small amounts of PIP2 did not affect the raft formation‚ and it showed remarkable affinity to lipid raft nanodomains. Simulations of the signaling transmembrane protein CD3ε in our raft-forming membranes were further performed to study the protein-lipid interaction as well. Results showed that the cytoplasmic tail of CD3ε was recruited to the Lo/ Ld boundary due to PIP2 binding‚ and this binding was regulated by Ca

High Quality Factor Enabled by Multiscale Phonon Scattering for Enhancing Thermoelectrics in Low-Solubility n-Type PbTe-Cu2Te Alloys.

The fundamental challenge for enhancing the thermoelectric performance of n-type PbTe to match p-type counterparts is to eliminate the Pb vacancy and reduce the lattice thermal conductivity. The Cu atom has shown the ability to fill the cationic vacancy, triggering improved mobility. However, the relatively higher solubility of Cu2Te limits the interface density in the n-type PbTe matrix, leading to a higher lattice thermal conductivity. In particular, a quantitative relationship between the precipitate scattering and the reduction of lattice thermal conductivity in the n-type PbTe with low solubility of Cu2Te alloys still remains unclear. In this work, trivalent Sb atoms are introduced, aiming at decreasing the solubility of Cu in PbTe for improving the precipitate volumetric density and ensuring n-type degenerate conduction. Benefiting from the multiscale hierarchical microstructures by Sb and Cu codoping, the lattice thermal conductivity is considerably decreased to 0.38 W m-1 K-1. The Debye-Callaway model quantifies the contribution from point defects and nano/microscale precipitates. Moreover, the mobility increases from 228 to 948 cm2 V-1 s-1 because of the elimination of cationic vacancies. Consequently, a high quality factor is obtained, enabling a superior peak figure of merit ZT of ∼1.32 in n-type Pb0.975Sb0.025Te by alloying with only ∼1.2% Cu2Te. The present finding demonstrates the significant role of low-solubility Cu2Te in advancing thermoelectrics in n-type PbTe.

Optimized Strategies for Advancing n-Type PbTe Thermoelectrics: A Review.

p-Type and n-type thermoelectric semiconductor materials with compatible performance are key components for thermoelectric devices. Great improvement in thermoelectric performance has been achieved in p-type PbTe, whereas the n-type counterpart still shows much inferior thermoelectric performance compared to that of the p-type PbTe. This inspires many strategies focused on advancing n-type PbTe thermoelectrics. Herein, not only effective mass engineering, resonance states, point defects, and nanostructures but also newly developed concepts including dynamic doping for stabilizing the optimal carrier concentration and introducing dislocations for reducing lattice thermal conductivity are summarized. In addition, the synergistic effects for further enhancing the thermoelectric performance are outlined, together with a discussion and outlook for boosting the advancement in n-type PbTe thermoelectric materials. Strategies discussed here are expected to be applicable to other thermoelectric materials.

Superconductivity related to the suppression of exciton formation in 1T-TiSe2.

In strongly correlated electron system, the impact of elementary substitution or intercalation plays a crucial role in determining electronic ground state among various macroscopic quantum phases such as charge order and superconductivity. Here, we report that simultaneous Cu intercalation and Ta substitution at Ti site in 1T-Cu x Ti0.8Ta0.2Se2 induce an intrinsic electronic phase diagram, characterized by an inherent superconducting transition in the x region of 0 ⩽ x ⩽ 0.12, with a maximum superconducting transition temperature T c of 2.5 K for x = 0.04, in contrast to the non-superconducting sample 1T-Cu0.04TiSe2. The increased density of free charge carriers screen the Coulomb interaction between electron-hole pairs effectively, promoting the occurrence of superconductivity favourably. Present results suggest that the Cu intercalation and the Ta substitution-induced suppression of the exciton condensation boost the superconductivity, shedding new light on the fundamental physics of the interplay between superconductivity, charge order, and electron correlation.