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Abstract Grain boundary plays a vital role in thermoelectric transports, leading to distinct properties between single crystals and polycrystals. Manipulating the grain boundary to realize good thermoelectric properties in polycrystals similar as those of single crystals is a long-standing task, but it is quite challenging. Herein, we develop a liquid-phase sintering strategy to successfully introduce Mg2Cu nano-sintering-aid into the grain boundaries of Mg3(Bi, Sb)2-based materials. The nano-aid helps to enlarge the average grain size to 23.7 μm and effectively scatter phonons, leading to excellent electrical transports similar as those of single crystals and ultralow lattice thermal conductivity as well as exceptional thermoelectric figure of merit (1.5 at 500 K) and conversion efficiency (7.4% under temperature difference of 207 K). This work provides a simple but effective strategy for the fabrication of high-performance polycrystals for large-scale applications.

The effectiveness of steel fibres in improving mortar is closely related to their length and dosage To investigate the effect of different lengths and dosages of steel fibres on the performance of mortar, four lengths of steel fibres, namely 6 mm, 13 mm, 25 mm, and 30 mm, were selected, and each length of fibre was single-mixed and multi-mixed following the volumetric rates of 0.5%, 1%, 1.5%, and 2%. The frost resistance of the steel fibre mortar was also analysed by freeze-thaw cycles regarding the compressive strength and flexural strength loss rate. The results showed that the compressive strength of the specimens was significantly improved as the four lengths of fibres were mixed in equal proportions of 1%. The flexural strength was most obviously increased when the four lengths of fibres were mixed in equal proportions of 1.5%, and the compression-flexural ratio was the smallest. At this time, the mortar had the best comprehensive performance. It was also found that the mixing the different lengths of steel fibres at a dosage of 1%∼1.5% in equal proportions resulted in a more uniform distribution of fibres. It improved the mortar better than the single mixing. After the 100 freeze-thaw cycle tests, the loss rate of the steel fibre mortar specimen was significantly lower than the ordinary mortar specimen. Mixing different lengths of steel fibres can improve the mechanical properties and frost resistance of the mortar more effectively.

Abstract Critical phenomena are one of the most captivating areas of modern physics, whereas the relevant experimental and theoretical studies are still very challenging. Particularly, the underlying mechanism behind the anomalous thermoelectric properties during critical phase transitions remains elusive, i.e., the current theoretical models for critical electrical transports are either qualitative or solely focused on a specific transport parameter. Herein, we develop a quantitative theory to model the electrical transports during critical phase transitions by incorporating both the band broadening effect and carrier-soft TO phonon interactions. It is found that the band-broadening effect contributes an additional term to Seebeck coefficient, while the carrier—soft TO phonon interactions greatly affects both electrical resistivity and Seebeck coefficient. The universality and validity of our model are well confirmed by experimental data. Furthermore, the features of critical phase transitions are effectively tuned. For example, alloying S in Cu2Se can reduce the phase transition temperature but increase the phase transition parameter b. The maximum thermoelectric figure of merit zT is pushed to a high value of 1.3 at the critical point (377 K), which is at least twice as large as those of normal static phases. This work not only provides a clear picture of the critical electrical transports but also presents new guidelines for future studies in this exciting area.

Abstract The flexible thermoelectric technique, which can convert heat from the human body to electricity via the Seebeck effect, is expected to provide a peerless solution for the power supply of wearables. The recent discovery of ductile semiconductors has opened a new avenue for flexible thermoelectric technology, but their power factor and figure-of-merit values are still much lower than those of classic thermoelectric materials. Herein, we demonstrate the presence of morphotropic phase boundary in Ag2Se-Ag2S pseudobinary compounds. The morphotropic phase boundary can be freely tuned by adjusting the material thermal treatment processes. High-performance ductile thermoelectric materials with excellent power factor (22 μWcm−1 K−2) and figure-of-merit (0.61) values are realized near the morphotropic phase boundary at 300 K. These materials perform better than all existing ductile inorganic semiconductors and organic materials. Furthermore, the in-plane flexible thermoelectric device based on these high-performance thermoelectric materials demonstrates a normalized maximum power density reaching 0.26 Wm−1 under a temperature gradient of 20 K, which is at least two orders of magnitude higher than those of flexible organic thermoelectric devices. This work can greatly accelerate the development of flexible thermoelectric technology.

In order to explore the ability of pre-treated rice husk ash concrete to resist acid rain erosion, this study investigates the deterioration law of ordinary concrete and pre-treated rice husk ash concrete under the combined action of acid rain erosion and dry-wet cycles, combining microscopic changes and a series of indicators such as the compressive strength of the concrete, with the dry-wet cycle of clean water as a control to analyse the deterioration law of the concrete. The results show that when the replacement rate of the pre-treated rice husk ash is 10%, the compressive strength of the concrete is the most improved and the splitting tensile strength is negatively correlated with the substitution rate of P-RHA. From the durability of the concrete, with the progress of the dry-wet cycle, the mass, compressive strength, and relative dynamic elasticity modulus show a decreasing trend, and the water absorption shows an upward trend. According to microscopic changes, the two types of concrete are mainly eroded by gypsum. The addition of P-RHA can promote the growth of C-S-H gels, reduce the effective porosity of the concrete, and delay the deterioration time of the concrete. By analysing the depth of the degradation of the concrete′s compressive strength, it is concluded that the ordinary concrete is destroyed earlier than the P-RHA concrete.

With advancements in chip technology, the number of cores in modern commercial processors continues to rise, leading to increased complexity in interconnects and on-chip networks. This complexity, however, exposes significant security vulnerabilities, primarily in the form of side-channel and covert-channel exploits. Unlike other microarchitectural side-channel attacks, those leveraging on-chip interconnects utilize unique characteristics, allowing attackers to develop novel methods that can bypass existing effective defenses. In this paper, we present a comprehensive survey of current side-channel and covert-channel attacks based on processor-on-chip interconnects. We categorize these attacks into three types: contention-based, distance-based, and layout-based, according to the specific interconnect characteristics they exploit, and discuss corresponding countermeasures for each. Finally, we provide an outlook on future development trends in processor interconnect side channels. This survey is the first to specifically focus on interconnect-based side channels in processors.

Calcium peroxide (CP) is an oxidizing agent that can gradually release hydrogen peroxide (HP) to achieve selective killing of cyanobacteria in water blooms, and reduce the phosphorus content in the water column. Despite the potential of CP for use in cyanobacterial water bloom disposal, there is a lack of research on the mechanism of oxidative damage on cyanobacterial cells by calcium peroxide. Further studies are required to comprehend the underlying scientific principles and potential risks and benefits of applying this approach to cyanobacteria disposal. In this investigation, we employed varying doses of CP for the treatment of Microcystis aeruginosa (M. aeruginosa), which resulted in the following findings: (1) the HP released from CP can damage the photosystem II of M. aeruginosa, reduce cell photosynthetic pigment content, intensify the degree of membrane lipid peroxidation, and increase the extracellular protein content; (2) CP significantly increased the soluble extracellular polysaccharide (sEPS) and bound extracellular polysaccharide (bEPS) content of cells (p

Objective: Neoadjuvant therapy (NAT) has been widely implemented as an essential treatment to improve therapeutic efficacy in patients with locally-advanced cancer to reduce tumor burden and prolong survival, particularly for human epidermal growth receptor 2-positive and triple-negative breast cancer. The role of peripheral immune components in predicting therapeutic responses has received limited attention. Herein we determined the relationship between dynamic changes in peripheral immune indices and therapeutic responses during NAT administration. Methods: Peripheral immune index data were collected from 134 patients before and after NAT. Logistic regression and machine learning algorithms were applied to the feature selection and model construction processes, respectively. Results: Peripheral immune status with a greater number of CD3+ T cells before and after NAT, and a greater number of CD8+ T cells, fewer CD4+ T cells, and fewer NK cells after NAT was significantly related to a pathological complete response (P < 0.05). The post-NAT NK cell-to-pre-NAT NK cell ratio was negatively correlated with the response to NAT (HR = 0.13, P = 0.008). Based on the results of logistic regression, 14 reliable features (P < 0.05) were selected to construct the machine learning model. The random forest model exhibited the best power to predict efficacy of NAT among 10 machine learning model approaches (AUC = 0.733). Conclusions: Statistically significant relationships between several specific immune indices and the efficacy of NAT were revealed. A random forest model based on dynamic changes in peripheral immune indices showed robust performance in predicting NAT efficacy.

Bi2Te3-based alloys are the most mature commercial thermoelectric (TE) materials for the cooling application near room temperature. However, the poor mechanical properties of the commercial zone melting (ZM) ingot severely limits the further application. Meanwhile, due to the donor-like effect, the robust polycrystalline n-type bulks usually have low TE performance near room temperature. Herein, based on the commercial ZM ingots, a high figure of merit (zT) of 1.0 at 320 K and good mechanical properties are achieved via the hot extrusion. The dynamic recrystallization in the hot-extrusion process can suppress the donor-like effect and refine the large ZM grains into fine-equiaxed grains. Moreover, the obtained polycrystalline Bi2Te2.79Se0.21 has good preferential orientation and high carrier mobility (μ). The high μ and the weaken donor-like effect maintain the high power factor (PF) of 43.1 μW cm−1 K−2 in the hot-extruded ZM sample. Due to the enhanced phonon scattering, the total thermal conductivity κtot decreased to 1.35 W·m−1·K−1. To demonstrate the good mechanical properties of the extruded ZM sample, micro TE dices with the cross sections of 300 μm × 300 μm and 200 μm × 200 μm are successfully cut from the extrusion sample. This study provided a fast and low-cost extrusion technique to improve the TE and mechanical properties of the commercial ZM ingot at room temperature.

Abstract Purpose Despite the poor prognosis of triple-negative breast cancer (TNBC), it has been demonstrated that neoadjuvant immunotherapy in combination with chemotherapy can improve the pathologic complete response (pCR) rate and/or long-term outcome of TNBC. However, there have been no real-world studies reporting on the effectiveness of neoadjuvant checkpoint inhibitors in early TNBC. Methods Between November 2019 and December 2021, 63 early TNBC patients treated with anti-PD-1 antibodies (pembrolizumab or camrelizumab) or anti-PD-L1 antibody (atezolizumab) in combination with chemotherapy at seven institutions were included. PCR1 defined as ypT0/Tis and ypN0 was the primary endpoint. Secondary endpoints included pCR2 defined as ypT0/Tis, overall response rate (ORR), disease-free survival (DFS), drug-related adverse events (AEs) and biomarkers. Results Among the patients in the current study, 34.9% of patients were able to achieve pCR1, and 47.6% of patients had achieved pCR2. The ORR was 82.5%. 33 patients with non-pCR2 tumors were found to have a median DFS of 20.7 months (95% CI 16.3 months-not reached). The DFS of patients with pCR2 and non-pCR2 after neoadjuvant therapy was significantly different (HR = 0.28, 95% CI 0.10–0.79; P = 0.038). The most common AEs were nausea (63.4%), fatigue (42.7%), leucopenia (30.0%) and elevated transaminase (11.7%). Conclusion It is possible to achieve a meaningful pCR rate and DFS by combining neoadjuvant checkpoint blockade with chemotherapy in patients with high-risk TNBC. Compared to clinical trials, however, there was a slightly lower pCR rate in this multicentered real-world study.

It is still challenging to discover plastically deformable inorganic semiconductors. Here, the authors report a high-throughput screening of tens of potential 2D van der Waals crystals that can deform plastically accompanied with experimental verification.

Today solid-state cooling technologies below 77 K are greatly limited. Here, the authors report the colossal Nernst power factor in NbSb2 single crystal, providing a high performance thermomagnetic material for solid-state cooling at low temperature.

AgSbTe2-based ternary chalcogenides show excellent thermoelectric performance at low- and middle-temperature ranges, yet their practical applications are greatly limited by their intrinsic poor thermodynamic stability. In this work, we demonstrate that AgSbTe2-based ternary chalcogenides can be stabilized for service below their decomposition threshold. A series of AgxSb2-xTe3-x (x = 1.0, 0.9, 0.8 and 0.7) samples have been prepared by the melt-quenching method. Among them, phase pure Ag0.9Sb1.1Te2.1 is verified by comprehensive structural characterizations from macroscale by X-ray diffraction to microscale by energy-dispersive spectroscopy and then to sub-nanometer scale by atom probe tomography. This composition is further chosen for the stability investigation. The decomposition threshold of Ag0.9Sb1.1Te2.1 appears around 473 K. Below this temperature, the chemical compositions and thermoelectric properties are barely changed even after 720 h annealing at 473 K. The figure-of-merit (zT) value of Ag0.9Sb1.1Te2.1 below the decomposition threshold is very competitive for real applications even compared with Bi2Te3-based alloys. The average zT of Ag0.9Sb1.1Te2.1 at 300–473 K reaches 0.84, which is higher than most other thermoelectric materials in a similar temperature range, promising applications in miniaturized refrigeration and power generation near room temperature.

IntroductionTaste and odor (T&O) problems have been affecting drinking water safety. As a eutrophicated drinking water reservoir in Tianjin city, the Yuqiao Reservoir was threatened by 2-MIB and geosmin in recent years.MethodsIn this study, quantile regression analysis and metagenome were used to quickly and accurately screen the producers and drivers of 2-MIB and geosmin in this reservoir.ResultsThe mean concentrations of 2-MIB and geosmin in the four-year were 103.58 ± 128.13 ng/L and 14.29 ± 27.95 ng/L, respectively. 2-MIB concentrations were higher in summer and autumn, with a bimodal variation throughout the year. Geosmin concentrations showed a decreasing trend from year to year from 2018 to 2021. Metagenome revealed that Pseudanabaena sp. dqh15, Microcoleus pseudautumnalis Ak1609, Pseudanabaena limnetica, and Planktothricoides raciborskii were the 2-MIB-producers, while Streptosporangium caverna and Dolichospermum circinale were the geosmin-producers. Multivariate quantile regression analysis indicated Pseudanabaena sp. and CODMn were the best predictors of 2-MIB concentrations, temperature and CODMn were the most useful parameters for describing geosmin concentration change. 2-MIB concentrations increased with the increase of Pseudanabaena sp. cell density and CODMn. Geosmin concentrations were higher at harsh temperatures and increased with higher CODMn. CODMn was significantly and positively correlated with the biosynthesis of secondary metabolites synthesis and terpenoid backone biosynthesis pathway. Both quantile regression and metagenome results showed that CODMn was an important driver of odor compounds.DiscussionMetagenome achieved higher resolution of taxonomic annotation than amplicons to identify odor-producers, which helps us to understand the main taxa of odor-producing microorganisms in Chinese water bodies and the genetic basis of odor compounds in microorganisms. Understanding the sources and drivers of odor compounds was useful for improving taste and odor problem management. This is the first time that the main odor-producing microorganisms in water bodies have been resolved by microbial metagenomic functional gene prediction.

Summary: Neoadjuvant therapy (NAT) is currently recommended to patients with human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) that typically exhibit a poor prognosis. The tumor immune microenvironment profoundly affects the efficacy of NAT. However, the correlation between tumor-infiltrating lymphocytes or their specific subpopulations and the response to NAT in HER2+ BC remains largely unknown. In our study, the immune infiltration status of 295 patients was classified as “immune-rich” or “immune-poor” phenotypes. The “immune-rich” phenotype was significantly positively related to pathological complete response (pCR). Ten genes were correlated with both pCR and the immune phenotype based on the results of spline and logistic regression. We constructed a generalized non-linear model combining linear and non-linear gene effects and successfully validated its predictive power using an internal and external validation set (AUC = 0.819, 0.797; respectively) and a clinical set (accuracy = 0.75).

By virtue of the excellent plasticity and tunable transport properties, Ag2S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications. Among them, Ag2S1-xTex exhibits rich and interesting variations in crystal structure, mechanical and thermoelectric transport properties. However, Te alloying obviously introduces extremely large order-disorder distributions of cations and anions, leading to quite complicated crystal structures and thermoelectric properties. Detailed composition-structure-performance correlation of Ag2S1-xTex still remains to be established. In this work, we designed and prepared a series of Ag2S1-xTex (x = 0–0.3) materials with low Te content. We discovered that the monoclinic-to-cubic phase transition occurs around x = 0.16 at room temperature. Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition, which is analyzed based on the thermodynamic principles. Compared with the monoclinic counterparts, the cubic-structured phases are more ductile and softer in mechanical properties. In addition, the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance. A maximum zT = 0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag2S0.7Te0.3. This work provides a useful guidance for designing Ag2S-based alloys with enhanced plasticity and high thermoelectric performance.

Abstract The recently discovered ductile/plastic inorganic semiconductors pave a new avenue toward flexible thermoelectrics. However, the power factors of current ductile/plastic inorganic semiconductors are usually low (below 5 µW cm−1 K−2) as compared with classic brittle inorganic thermoelectric materials, which greatly limit the electrical output power for flexible thermoelectrics. Here, large plasticity and high power factor in bulk two‐dimensional van der Waals (2D vdW) single‐crystalline SnSe2 are reported. SnSe2 crystals exhibit large plastic strains at room temperature and they can be morphed into various shapes without cracking, which is well captured by the inherent large deformability factor. As a semiconductor, the electrical transport properties of SnSe2 can be readily tuned in a wide range by doping a tiny amount of halogen elements. A high power factor of 10.8 µW cm−1 K−2 at 375 K along the in‐plane direction is achieved in plastic single‐crystalline Br‐doped SnSe2, which is the highest value among the reported flexible inorganic and organic thermoelectric materials. Combining the good plasticity, excellent power factors, as well as low‐cost and nontoxic elements, bulk 2D vdW single‐crystalline SnSe2 shows great promise to achieve high power density for flexible thermoelectrics.

Upon uniaxial compressive loading at 500 °C (T/Tm = 0.67, where Tm is the absolute melting point), the n-type Skutterudite alloy Yb0.3Co4Sb12 deforms plastically by creep via a power-law, with a stress exponent ∼3 consistent with dislocation viscous glide. An activation energy of 171 kJ/mol is measured over the temperature range of 500–587 °C (T/Tm = 0.67–0.75) at a stress of 30 MPa. Yb0.3Co4Sb12 is ductile at 500 °C, exhibiting a compressive strain of 25% when subjected to stresses ranging from 22 to 90 MPa for up to 28 days. Among the thermoelectric materials tested so far for creep, Yb0.3Co4Sb12 exhibits a creep resistance intermediate between low-melting (Bi2Te3, TAGS-85) and high-melting thermoelectrics (Mg2Si and ZrNiSn). A relatively modest drop in the figure of merit zT, from 0.67 to 0.52, is displayed by Yb0.3Co4Sb12 after accumulating 3.7% compressive creep strain at 500 °C, mostly due to a drop in electrical conductivity.

Flexible thermoelectrics, including flexible thermoelectric materials and devices, can directly convert the heat from human body into useful electricity, providing a promising solution for uninterrupted power to wearables. In the past decade, flexible thermoelectrics has achieved notable progress. Various kinds of flexible thermoelectric materials have been developed and some of them have been fabricated into flexible thermoelectric devices, showing the ability to generate nW‐level or even μW‐level electricity. Herein, the basic design principles and typical configurations of flexible thermoelectric devices, as well as the requirements on thermoelectric materials to achieve high performance flexible thermoelectric devices, are first introduced. Then, the recent progress achieved in flexible thermoelectric devices based on organics materials, traditional inorganic materials, other organic/inorganic composites/hybrids, and plastic deformable inorganic semiconductors, respectively, are summarized. Finally, an outlook on the future development of flexible thermoelectrics is briefly given. This study sheds light on the further development of flexible thermoelectrics.

Objective: To investigate the effect of anatomic and technical parameters on the incidental internal mammary lymph node (IMN) irradiation (IIMNI) dose among postmastectomy patients.Methods: We retrospectively delineated the IMN on planning CT images from 138 patients who had undergone postmastectomy radiotherapy (PMRT). We analyzed the IIMNI dose coverage and its relationship with anatomic and technical parameters.Results: The IIMNI mean dose was 32.85 ± 9.49 Gy, and 10 of 138 patients (7.25%) treated with PMRT received ≥45 Gy. In univariate analysis, the body weight, body mass index, body surface area, thoracic transverse diameter (DT), ratio of DT to the thoracic anteroposterior diameter (DAP)(RT/AP), planning target volume of IMN (PTVIMN) included in PTV (IMNin) and the ratio of IMNin to PTVIMN (RIMNin) and PTV posterior border were the parameters affecting IIMNI dose. In multivariate analysis, body weight, RT/AP, and RIMNin were correlative factors that affected IIMNI dose.Conclusions: For patients who underwent PMRT without IMN irradiation (IMNI), there was a wide variety in IIMNI doses. A minority of patients had adequate IIMNI dose coverage, and the higher IIMNI doses were associated with the less body weights and more RIMNin.

Self-powered wearable electronics require thermoelectric materials simultaneously with a high dimensionless figure of merit (zT) and good flexibility to convert the heat discharged by the human body into electricity. Ag2(S,Se)-based semiconducting materials can well satisfy these requirements, and thus, they are attracting great attention in thermoelectric society recently. Ag2(S,Se) crystalizes in an orthorhombic structure or monoclinic structure, depending on the detailed S/Se atomic ratio, but the relationship between its crystalline structure and mechanical/thermoelectric performance is still unclear to date. In this study, a series of Ag2Se1‐xSx (x=0, 0.1, 0.2, 0.3, 0.4, and 0.45) samples were prepared and their mechanical and thermoelectric performance dependence on the crystalline structure was systematically investigated. x=0.3 in the Ag2Se1‐xSx system was found to be the transition boundary between orthorhombic and monoclinic structures. Mechanical property measurement shows that the orthorhombic Ag2Se1‐xSx samples are brittle while the monoclinic Ag2Se1‐xSx samples are ductile and flexible. In addition, the orthorhombic Ag2Se1‐xSx samples show better electrical transport performance and higher zT than the monoclinic samples under a comparable carrier concentration, most likely due to their weaker electron-phonon interactions. This study sheds light on the further development of flexible inorganic TE materials.

Abstract Liquid‐like materials are one family of promising thermoelectric materials discovered in the past years due to their advantanges of ultrahigh thermoelectric figure of merit (zT), low cost, and environmental friendliness. However, their practial applications are greatly limited by the low service stability from the Cu/Ag metal deposition under large current and/or temperature gradient. Both high zT for high efficiency and large critical voltage for good stability are required for liquid‐like materials, but they are usually strongly correlated and hard to be tuned individually. Herein, based on the thermodynamic analysis, it is shown that such a correlation can be decoupled through doping immobile ions into the liquid‐like sublattice. Taking Cu2−δS as an example, doping immobile Fe ions in Cu1.90S scarcely degrades the initial large critical voltage, but significantly enhances the zT to 1.5 at 1000 K by tuning the carrier concentration to the optimal range. Combining the low‐cost and environmentally friendly features, these Fe‐doped Cu2−δS‐based compounds show great potential in civil applications. This study sheds light on the realization of both good stability and high performance for many other liquid‐like thermoelectric materials that have not been considered for real applications before.

Mixed ionic–electronic conductors are limited by material decomposition. Here the authors reveal the mechanism for atom migration and deposition in Cu2–δ (S,Se) materials based on a critical chemical potential difference and propose electronically conducting, ion-blocking interfaces to enhance stability.

Abstract Diamond‐like compounds are a promising class of thermoelectric materials, very suitable for real applications. However, almost all high‐performance diamond‐like thermoelectric materials are p‐type semiconductors. The lack of high‐performance n‐type diamond‐like thermoelectric materials greatly restricts the fabrication of diamond‐like material‐based modules and their real applications. In this work, it is revealed that n‐type AgInSe2 diamond‐like compound has intrinsically high thermoelectric performance with a figure of merit (zT) of 1.1 at 900 K, comparable to the best p‐type diamond‐like thermoelectric materials reported before. Such high zT is mainly due to the ultralow lattice thermal conductivity, which is fundamentally limited by the low‐frequency Ag‐Se “cluster vibrations,” as confirmed by ab initio lattice dynamic calculations. Doping Cd at Ag sites significantly improves the thermoelectric performance in the low and medium temperature ranges. By using such high‐performance n‐type AgInSe2‐based compounds, the diamond‐like thermoelectric module has been fabricated for the first time. An output power of 0.06 W under a temperature difference of 520 K between the two ends of the module is obtained. This work opens a new window for the applications using the diamond‐like thermoelectric materials.

In this study, a series of copper sulfides CuxS with x spanning from 1.8 to 1.96 was prepared and their crystal structures, elemental valence states, and thermoelectric properties were systematically studied. The valence state of Cu in CuxS is unchanged as the ratio of Cu/S varies, while the thermoelectric properties are very sensitive to the deficiency of Cu. In addition, the type of sulfur arrangement in the crystal structure also plays an important role on the electrical transports. Finally, the optimum Cu/S atomic ratios in the binary CuxS system were identified for high power factor and thermoelectric figure of merit.

For filled skutterudites, element Yb is one of the most common and important fillers. However, the optimal carrier concentration range in Y bxCo4Sb12 filled skutterudites has not been determined as a result of the low Yb filling fraction limit. In this study, a non-equilibrium fabrication process (MS-SPS process), consisting of a melt-spinning method and a spark plasma sintering technique, has been applied to prepare Y bxCo4Sb12 samples. The Yb filling fraction is successfully extended to 0.35, which provides the possibility to clarify the optimal carrier concentration range for Yb-filled skutterudites. High carrier concentrations, with a maximum of around 1 × 1021 cm−3, were achieved in the MS-SPS Y bxCo4Sb12 samples due to the significantly enhanced Yb filling fractions. The phase compositions, lattice parameters, electrical and thermal transport properties of the MS-SPS Y bxCo4Sb12 samples with high carrier concentrations were systematically investigated. An optimal carrier concentration range of around 5 ∼ 6 × 1020 cm−3, corresponding to the actual Yb filling fraction of around 0.21∼0.26, has been determined, which displays the highest thermoelectric performance in Y bxCo4Sb12 thermoelectric materials.