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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.

Enhancing the adaptability of Unmanned Aerial Vehicle (UAV) swarm control models to cope with different complex working scenarios is an important issue in this research field. To achieve this goal, control model with tunable parameters is a widely adopted approach. In this article, an improved UAV swarm control model with tunable parameters namely Multi-Objective O-Flocking (MO O-Flocking) is proposed. The MO O-Flocking model is a combination of a multi rule control system and a virtual-physical-law based control model with tunable parameters. To achieve multi-objective parameter tuning, a multi-objective parameter tuning method namely Improved Strength Pareto Evolutionary Algorithm 2 (ISPEA2) is designed. Simulation experiment scenarios include six target orientation scenarios with different kinds of objectives. Experimental results show that both the ISPEA2 algorithm and MO O-Flocking control model have good performance in their experiment scenarios.

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.

Abstract Following the Materials Genome Initiative project, materials research has embarked a new research paradigm centered around material repositories, significantly accelerating the discovery of novel materials, such as thermoelectrics. Thermoelectric materials, capable of directly converting heat into electricity, are garnering increasing attention in applications like waste heat recovery and refrigeration. To facilitate research in this emerging paradigm, we have established the Materials Hub with Three‐Dimensional Structures (MatHub‐3d) repository, which serves as the foundation for high‐throughput (HTP) calculations, property analysis, and the design of thermoelectric materials. In this review, we summarize recent advancements in thermoelectric materials powered by the MatHub‐3d, specifically HTP calculations of transport properties and material design on key factors. For HTP calculations, we develop the electrical transport package for HTP purpose, and utilize it for materials screening. In some works, we investigate the relationship between transport properties and chemical bonds for particular types of thermoelectric compounds based on HTP results, enhancing the fundamental understanding about interested compounds. In our work associated with material design, we primarily utilize key factors beyond transport properties to further expedite materials screening and speedily identify specific materials for further theoretical/experimental analyses. Finally, we discuss the future developments of the MatHub‐3d and the evolving directions of database‐driven thermoelectric research.

Abstract The study of thermoelectric behaviors in miniatured transistors is of fundamental importance for developing bottom-level thermal management. Recent experimental progress in nanothermetry has enabled studies of the microscopic temperature profiles of nanostructured metals, semiconductors, two-dimensional material, and molecular junctions. However, observations of thermoelectric (such as nonequilibrium Peltier and Thomson) effect in prevailing silicon (Si)—a critical step for on-chip refrigeration using Si itself—have not been addressed so far. Here, we carry out nanothermometric imaging of both electron temperature (T e) and lattice temperature (T L) of a Si nanoconstriction device and find obvious thermoelectric effect in the vicinity of the electron hotspots: When the electrical current passes through the nanoconstriction channel generating electron hotspots (with T e~1500 K being much higher than T L~320 K), prominent thermoelectric effect is directly visualized attributable to the extremely large electron temperature gradient (~1 K/nm). The quantitative measurement shows a distinctive third-power dependence of the observed thermoelectric on the electrical current, which is consistent with the theoretically predicted nonequilibrium thermoelectric effects. Our work suggests that the nonequilibrium hot carriers may be potentially utilized for enhancing the thermoelectric performance and therefore sheds new light on the nanoscale thermal management of post-Moore nanoelectronics.

Unsatisfied electrode bonding in half-Heusler devices limits their practical service at high temperatures. Here, the authors develop a direct bonding interface to ideal ohmic contact and thermally inert and ohmic contact, leading to high deficiency.

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.

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 With the increasing building energy consumption, building integrated photovoltaic has emerged. However, this method has problems such as low photovoltaic absorption rate and large load peak–valley difference. For this reason, the authors have constructed a building integrated photovoltaic‐phase change material system considering the demand response. Under the demand response at the time of use, the system was powered by building photovoltaic power generation. The thermostatically controlled load demand inside buildings was satisfied jointly by the phase change energy storage and the air conditioning. The system can run offline or connected to the grid through surplus electricity. When electricity is insufficient, the system can purchase it from the grid. The system dispatching strategy is also given. Based on the principles of minimising the daily cost of system operation, maximising the photovoltaic absorption rate, and minimising the peak–valley difference, a multi‐objective optimisation model is established, and the particle swarm algorithm is used to perform the capacity configuration on the energy storage system. Finally, case analysis was conducted to verify that the scheme is able to reduce the system operating cost by over 50%. In addition, it can greatly increase the photovoltaic absorption rate and reduce the peak–valley difference to achieve peak load shifting. The scheme has significant economic and technical benefits.

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.

Background and aimsThe epidemiological characteristics of MAFLD and its relationship with atrial fibrillation (AF) are limited in China. Therefore, we explored the epidemiological characteristics of MAFLD from adults along with the association of MAFLD and 12-ECG diagnosed AF in a nationwide population from health check-up centers.MethodsThis observational study used cross-sectional and longitudinal studies with 2,083,984 subjects from 2009 to 2017. Age-, sex-, and regional-standardized prevalence of MAFLD was estimated. Latent class analysis (LCA) was used to identify subclusters of MAFLD. Multivariable logistic regression and mixed-effects Cox regression models were used to analyze the relationship between MAFLD and AF.ResultsThe prevalence of MAFLD increased from 22.75% to 35.58% during the study period, with higher rates in males and populations with high BMI or resided in northern regions. The MAFLD population was clustered into three classes with different metabolic features by LCA. Notably, a high proportion of MAFLD patients in all clusters had overweight and prediabetes or diabetes. The MAFLD was significantly associated with a higher risk of AF in the cross-sectional study and in the longitudinal study. In addition, the coexistence of prediabetes or diabetes had the largest impact on subsequent AF.ConclusionOur findings suggested a high prevalence of MAFLD and a high prevalence of other metabolic diseases in the MAFLD population, particularly overweight and glucose dysregulation. Moreover, MAFLD was associated with a significantly higher risk for existing and subsequent subclinical AF in the Chinese population.

Heat pumping is in high demand at cryogenic temperature, but whether thermoelectricity can take on cryogenic heat pumping is an open question. Here, the authors answer this question by leveraging bipolar effect to enhance transverse thermoelectricity in semimetal Mg2Pb for cryogenic heat pumping.

Metal halide perovskites (MHPs) hold great potential in thermoelectric (TE) applications, thanks to their regular and soft lattice in nature. However, the poor electrical conductivity caused by low charge carrier density (1019 cm−3). However, further electrical doping remains challenging, originating from the limited capability of accommodating heterogeneous dopants and the heavy compensation in THPs. Herein, a novel diffusion‐mediated doping approach is demonstrated to prominently increase the p‐type doping level of THPs by a sequence of air exposure and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) surface treatments. In paradigm photovoltaic THP materials—CH(NH2)2SnI3 (namely FASnI3), the electrical conductivity is dramatically increased by 300× from 0.06 to 18 S cm−1 in thin films, leading to a remarkable enhancement of power factor by 25× up to 53 μW m−1 K−2. In contrast, only a slight variation of thermal conductivity is observed after F4TCNQ deposition, which is in accordance with the increase in electrical conductivity, indicating that the lattice structures of FASnI3 remain intact after doping. This study paves an illuminating way to ameliorate TE properties in halide perovskites.

Long-term service stability of thermoelectric devices is one of the major obstacles for their application. Here, the authors combine interfacial reaction energy and Sb migration activation energy barrier as a criterion to determine the interfacial reliability for skutterudite thermoelectric devices.

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.

Abstract To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3Co4Sb12 samples were fabricated by melting–quenching–annealing–spark plasma sintering (SPS) method. Two sets of samples, before and after SPS, were investigated. In both the two sets of samples, the average grain size of the samples increases monotonously with the increase of annealing time, while Yb filling fraction firstly increases and then decreases. Yb not filling into the skutterudite remains at the grain boundaries in the form of Yb2O3 after SPS, which could be quantified by the spatially difference method of energy dispersive spectra. Step distribution of Yb filling fraction was observed in the samples annealed for 1 h, which was caused by the microstructural evolution from the peritectic phases to the skutterudite phase. The sample annealed for 3 days and SPS sintered possesses the maximum value of Yb filling fraction 0.249 and the maximum ZT value of 1.24 at 850 K. These results are helpful to better understand the microstructural evolution and Yb filling behavior in skutterudite materials.

A novel trench SOI LDMOS with centrosymmetric double vertical field plates structure (CDVFPT SOI LDMOS) is proposed in this paper. The 2-D device simulator MEDICI is used to investigate the characteristics of the proposed structure. Compared with the conventional trench SOI LDMOS (CT SOI LDMOS), the optimized device shows an obvious reduction in the specific on-resistance (Ron,sp) when its breakdown voltage (BV) is enhanced due to the introduction of centrosymmetric double vertical field plates structure. And when compared to previous device with floating vertical field plate trench SOI LDMOS (FVFPT SOI LDMOS), the overall performance of CDVFPT SOI LDMOS is also promoted. According to the simulation results, compared to a CT SOI LDMOS, the BV of CDVFPT SOI LDMOS increases from 188 V to 234 V. The Ron,sp, however, decreases from 2.30 mΩ·cm2 to 1.24 mΩ·cm2. In addition, the maximum lattice temperature at 1 mW/μm2 is slightly reduced. Keywords: Power MOSFET, Vertical field plate, Breakdown voltage, Specific on-resistance

Although flexible thermoelectric materials based on conducting polymers are attractive for energy harvesting, their performance is inferior to their inorganic counterparts. Here, the authors present a facile method to deliver inorganic nanowire films with high power factor and flexibility.

La3Te4-based rare-earth telluride is a kind of n-type high-temperature thermoelectric (TE) material with an operational temperature of up to 1273 K, which is a promising candidate for thermoelectric generators. In this work, the Sm substitution in La3−xSmxTe4/Ni composites is reported. The electrical transport property of La3−xSmxTe4 is modified by reducing carrier concentration due to the substitution of Sm2+ for La3+. The electric thermal conductivity decreases by 90% due to carrier concentration reduction, which mainly contributes to a reduction in total thermal conductivity. Lattice thermal conductivity also decreases by point-defect scattering by Sm doping. Meanwhile, based on our previous study, compositing nickel improves the thermal stability of the La3 − xSmxTe4 matrix. Finally, combined with carrier concentration optimization and the decreased thermal conductivity, a maximum zT of 1.1 at 1273 K and an average zTave value of 0.8 over 600 K–1273 K were achieved in La2.315Sm0.685Te4/10 vol.% Ni composite, which is among the highest TE performance reported in La3Te4 compounds.

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 Background Several studies have emerged indicating that sarcopenia is associated with nonalcoholic fatty liver disease, we aimed to systematically review and quantify the association between sacropenia and the histological severity of nonalcoholic fatty liver disease. Methods Pubmed, the Cochrane Library and EMBASE were searched (until August 2017) for studies examining the relationship of sarcopenia with steatohepatitis and advanced liver fibrosis in nonalcoholic fatty liver disease. Pooled odds ratios were estimated by fixed effects models. Results Three articles met our inclusion criteria, with a total of 3226 individuals. Two of the studies examined the association between sacropenia and steatohepatitis, a significant association was documented between sarcopenia and steatohepatitis (OR = 2.35, 95%CI 1.45, 3.81). All of the three studies assessed the association between sacropenia and advanced liver fibrosis, a significant association between sarcopenia and advanced liver fibrosis (OR = 2.41, 95%CI 1.94, 2.98). No significant heterogeneity was detected among studies in all comparisons. These results remained essentially unchanged after excluding any of the studies in the sensitivity analysis. Conclusions Sarcopenia in patients with nonalcoholic fatty liver disease is associated with a higher likelihood of having steatohepatitis or advanced liver fibrosis. Demonstration of the role of sarcopenia in nonalcoholic fatty liver disease development in future studies could have important therapeutic implications.

Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure–property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure–property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure–property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials.

The crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu2−xSe is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu2−xSe is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to the transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.

Precise localization and pose estimation in indoor environments are commonly employed in a wide range of applications, including robotics, augmented reality, and navigation and positioning services. Such applications can be solved via visual-based localization using a pre-built 3D model. The increase in searching space associated with large scenes can be overcome by retrieving images in advance and subsequently estimating the pose. The majority of current deep learning-based image retrieval methods require labeled data, which increase data annotation costs and complicate the acquisition of data. In this paper, we propose an unsupervised hierarchical indoor localization framework that integrates an unsupervised network variational autoencoder (VAE) with a visual-based Structure-from-Motion (SfM) approach in order to extract global and local features. During the localization process, global features are applied for the image retrieval at the level of the scene map in order to obtain candidate images, and are subsequently used to estimate the pose from 2D-3D matches between query and candidate images. RGB images only are used as the input of the proposed localization system, which is both convenient and challenging. Experimental results reveal that the proposed method can localize images within 0.16 m and 4° in the 7-Scenes data sets and 32.8% within 5 m and 20° in the Baidu data set. Furthermore, our proposed method achieves a higher precision compared to advanced methods.

The lattice dynamics and thermal transport in Cu2-δSe compounds were investigated via theoretical calculations, neutron measurement, and characterization of thermal properties. The results show that binary ordered Cu2-δSe has an extremely low lattice thermal conductivity at low temperatures. The low energy multi-Einstein optic modes are the dominant approach obtaining such an extremely low lattice thermal conductivity. It is indicated that the damped vibrations of copper ions could contribute to the low energy multi-Einstein optic modes, especially for those low energy branches at 2–4 meV.

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.

Polycrystalline SnSe was synthesized by a melting-annealing-sintering process. X-ray diffraction reveals the sample possesses pure phase and strong orientation along [h00] direction. The degree of the orientations was estimated and the anisotropic thermoelectric properties are characterized. The polycrystalline sample shows a low electrical conductivity and a positive and large Seebeck coefficient. The low thermal conductivity is also observed in polycrystalline sample, but slightly higher than that of single crystal. The minimum value of thermal conductivity was measured as 0.3 W/m·K at 790 K. With the increase of the orientation factor, both electrical and thermal conductivities decrease, but the thermopowers are unchanged. As a consequence, the zT values remain unchanged in the polycrystalline samples despite the large variation in the degree of orientation.

Ideal heat exchangers recover as much heat as possible from an engine exhaust at the cost of an acceptable pressure drop. They provide primary heat for a thermoelectric generator (TEG), and their capacity and efficiency is dependent on the material, shape, and type of the heat exchanger. Six different exhaust heat exchangers were designed within the same shell, and their computational fluid dynamics (CFD) models were developed to compare heat transfer and pressure drop in typical driving cycles for a vehicle with a 1.2 L gasoline engine. The result showed that the serial plate structure enhanced heat transfer by 7 baffles and transferred the maximum heat of 1737 W. It also produced a maximum pressure drop of 9.7 kPa in a suburban driving cycle. The numerical results for the pipe structure and an empty cavity were verified by experiments. Under the maximum power output condition, only the inclined plate and empty cavity structure undergoes a pressure drop less than 80 kPa, and the largest pressure drop exceeds 190 kPa. In this case, a mechanism with a differential pressure switch is essential to bypass part of the exhaust.

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.

To improve the interfacial stability at high temperatures, n-type skutterudite (SKD) thermoelectric joints with sandwich structures of Ti/Mo/Yb0.3Co4Sb12 were successfully designed and fabricated. In this structure, Mo and Ti were introduced as the barrier layer with the goal of suppressing the interfacial diffusion and the buffer layer with the goal of enhancing the bonding strength, respectively. To evaluate the high temperature interfacial behavior of the Ti/Mo/Yb0.3Co4Sb12 joints, thermal shocking between 0 °C and 600 °C and isothermal aging at a temperature range of 550 °C to 650 °C were carried out in vacuum. During the isothermal aging process, Ti penetrates across the Mo layer, and finally diffuses into the Yb0.3Co4Sb12 matrix. By increasing the isothermal aging time, Ti continuously diffuses and reacts with the elements of Sb and Co in the matrix, consequently forming the multilayer-structured intermetallic compounds of Ti3Sb/Ti2Sb/TiCoSb. Diffusion kinetics was investigated and it was found that the interfacial evolution of the Ti/Mo/Yb0.3Co4Sb12 joints was a diffusion-controlling process. During the diffusion process, the formed Mo-Ti buffer layer acts as a damper, which greatly decelerates the diffusion of Ti towards the Yb0.3Co4Sb12 matrix at high temperatures. Meanwhile, it was found that the increase in the contact resistivity of the joints mainly derives from the inter-diffusion between Ti and Yb0.3Co4Sb12. As a result, the Ti/Mo/Yb0.3Co4Sb12 joint demonstrates the excellent stability of the interfacial contact resistivity. Service life prediction was made based on the stability of the contact resistivity, and it was found that the Ti/Mo/Yb0.3Co4Sb12 joint is qualified for practical applications at 550 °C.