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Lithium-ion capacitors (LICs), which combine great power and energy density, have become promising energy storage and have been well studied recently. Developing novel battery-type anode materials is the key to mitigating the kinetic mismatch between the anode and cathode electrodes. In this paper, niobium diboride (NbB 2) nanoparticles are synthesized via a salt-templated method and proposed for the first time as the anodes for LICs. NbB 2 is a layered two-dimensional material similar to graphite, which is favorable to the intercalation and deintercalation of Li+. The NbB 2 with high conductivity delivers outstanding long cycling stability (254.1 mAh g−1 after 800 cycles at 0.1 A g−1) and great rate capability. Moreover, a high-performance LIC is assembled employing the prepared NbB 2 as anode and commercialized activated carbon (AC) as cathode, which can display an energy density of 68.76 Wh kg−1, a power density of 7.02 kW kg−1, and a capacity retention ratio of 98% after 10,000 cycles. The work presents the great potential of transition metal borides as electrode materials and accelerates the development of LICs. [Display omitted] • Niobium diboride are synthesized via a simple and facile molten salt method. • The NbB 2 nanoparticles are first reported as anodes for Lithium-ion capacitors. • The optimized NbB 2 electrode shows superior specific capacity and rate capability. • The surface capacitance dominates the NbB 2 electrode kinetics process. [ABSTRACT FROM AUTHOR]

Lead-free p-type AgSn 4 SbTe 6 based thermoelectric nanocomposites were fabricated by a process combining mechanical alloys (MA) and spark plasma sintering (SPS). It is found that dispersing SiC nanoparticles into the AgSn 4 SbTe 6 matrix can enhance the thermoelectric properties significantly. SiC nanoinclusions can increase the power factor mainly due to improved electrical conductivity while slightly increasing the Seebeck coefficient, in addition to reducing the thermal conductivity through enhancing phonon scattering. A high dimensionless figure of merit (ZT) value up to 1.0 at a relatively low temperature (723 K) is achieved in AgSn 4 SbTe 6 incorporated with a small amount (1 vol%) of SiC nanoparticles. This work validated the effectiveness of SiC nanodispersion in enhancing thermoelectric performance of AgSn 4 SbTe 6 , by which a simple process yields a high ZT equivalent to the record one reported for this materials fabricated by a melting process. [ABSTRACT FROM AUTHOR]

Abstract: The thermoelectric oxide AgSbO3 has been prepared by the conventional solid state reaction (CSSR) method combined with spark plasma sintering (SPS) technique. The electrical resistivity ρ and the Seebeck coefficient S were measured simultaneously from 323 to 873K. It was found that ρ decreased monotonically from 3.75 to 7.20×10−4 Ωm as the temperature was increased. The highest absolute value of the Seebeck coefficient |S| (S <0) reached 209μVK−1 at 873K. In addition to the large thermopower, a rather low thermal conductivity of 0.825Wm−1 K−1 at 873K has been observed. Better thermoelectric performance at higher temperatures may origin from the change in hybridization of the Ag 4d–O 2p orbital and the Ag 5s–Sb 5s orbital, which are responsible for engineering energy positions and shapes of the valence-band (VB) top and the conduction band (CB) bottom, respectively. [Copyright &y& Elsevier]

High concentration Nd3+-modified zeolite NaY with 22.6 wt% Nd element contained has been successfully prepared by a simple re-doping method via 4-fold ion-exchange and subsequent calcination treatments. This re-doping method not only provides a way to incorporate as high contend Nd cations within zeolite, but also proves the ion migration theory from experimental prospective. The obtained Nd-NaY zeolites are characterized by X-ray powder diffraction (XRD), Inductive coupled plasma (ICP), Scanning electron microscopy (SEM), etc, illustrating the Nd3+ cations can migrate into the sodalite cages from supercages, which leads to the lattice distortion of zeolite structure. With the addition of more Nd3+ ions, the average pore of the Nd-NaY zeolites has increased slowly while the specific surface area decreases. We found the values of reduce desorption activation energy (E d) of water decrease gradually with the introduction of Nd3+ cations when it used as adsorptive materials. When the Nd3+ content of zeolite reaches 22.6 wt %, the value of E d of water decreases to 154.7 kJ/mol. This research provides highly application value to reduce water molecules desorption activity energy as potential adsorptive materials in rotary dehumidification wheel. Image 1 • A simple efficient method for the preparation of high concentration Nd3+-modified NaY zeolites. • Nd3+ ions migrate into the sodalite cages from supercages. • More Nd ions can enter into the pores of zeolites by re-doping method. • Nd-NaY composites decrease the values of desorption activation energy of water molecules. [ABSTRACT FROM AUTHOR]

AgPb m SbTe m +2 (abbreviation as LAST) is a promising thermoelectric material based on PbTe for mid-temperature applications. The electrical and thermal transport properties of LAST alloys are greatly affected by the formation of nanostructured precipitation depending on the processing conditions, especially for spark plasma sintering (SPS) combined with mechanical alloying (MA). This study was focused on the optimization of SPS temperature ( T SPS ) and found that its variation in a narrow range (100 K) leads to apparent differences of thermoelectric performances. The sample sintered at an optimized temperature ( T SPS = 923 K) shows a low κ total (0.829 Wm −1 K −1 ) and a high PF (14.9 Wm −1 K −2 ), which is mainly attributed to the nanoscale composition segregation of Ag and Sb. The highest ZT value of 1.28 at 773 K was obtained when T SPS = 923 K, along with the highest ZT eng value of 0.26 and the corresponding η max value of 5.8% at the range of 323 K ( T cold )–773 K ( T hot ), which were increased almost twice by the optimization of sintering temperature. [ABSTRACT FROM AUTHOR]

The poor long-term cycle stability of cathode materials for aqueous zinc-ion batteries has always been one of the limiting factors affecting their further applications. In this work, a solvothermal method was used to change the morphology and structure of the V 2 O 5 precursor to prepare a curled hydrated VO 2 (B) nanosheet. The VO 2 (B) has a specific capacity of 400.2 mAh g−1 at 0.5 A g−1, and after 6,000 cycles at 5 A g−1, the VO 2 (B) can still achieve a discharge specific capacity of 223.5 mAh g−1, with a capacity retention rate of 84.3%. Moreover, the energy density and power density of the VO 2 (B) are also very impressive (300.7 Wh kg−1 at 168.61 W kg−1; 233.9 Wh kg−1 at 7317 W kg−1). Such excellent performance is closely linked to the suitable nanostructure, the high capacitance-controlled kinetic behavior, the fast diffusion of Zn2+ and the crystal water sustained the structure of VO 2 (B). And the energy storage mechanism of the material is H+/Zn2+ co-insertion. [Display omitted] • We used a solvothermal method converted V 2 O 5 to VO 2 (B)·0.25 H 2 O. • The cathode material got impressive energy density and power density. • The hydrated VO 2 (B) obtained for 223.5 mAh g−1 at 5 A g−1 after 6000 cycles. • Crystal water played a pillar role in the electrode material. • The H+/Zn2+ were co-inserted/extracted in the cathode material. [ABSTRACT FROM AUTHOR]

Abstract: CuFeS2 alloys composed of common and non-toxic elements were synthesized by combining mechanical alloying (MA) and spark plasma sintering (SPS). The CuFeS2 compound powders were synthesized directly by MA process, which were then spark plasma sintered to bulk materials. It was found that S content in the bulk samples became deficient depending on the fabrication conditions, and the ZT value improved slightly with decreasing S content. Under the optimized condition, CuFeS2− x (0 ⩽ x⩽ 0.25) samples were prepared to investigate the effect of S deficiency on the thermoelectric properties. The electrical resistivity and thermal conductivity decreased gradually with decreasing S content, resulting in a maximum ZT value of 0.21 at 573K for the sample CuFeS1.80. [Copyright &y& Elsevier]

Abstract: Both vacuum melting and mechanical alloying (MA) were applied to the fabrication of AgPb x SbTe20 (x =20, 21 and 22.5) as a promising thermoelectric material to investigate the processing influence on its thermoelectric properties. The AgPb x SbTe20 compound powders were prepared by pulverizing the melted ingots or directly from MA, which were then consolidated to fine-grained bulk materials by spark plasma sintering (SPS). A high ZT value of 1.25 at 725K was observed in the AgPb20SbTe20 samples fabricated by both methods. Thermoelectric properties of all AgPb x SbTe20 compounds synthesized by vacuum melting method are nearly the same as that of those fabricated by MA combined with SPS in the whole measured temperature range. Considering the complexity of the melting method but with the same results as the MA–SPS method, the present work revealed that the MA–SPS process is more suitable for the fabrication of PbTe-based thermoelectric materials. [Copyright &y& Elsevier]

Abstract: Highly dense n-type Bi2Te3 dispersed with x vol% nano-SiC particles (x =0, 0.1, 0.5, 1.0) thermoelectric materials were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS) method. The effects of nano-SiC addition on the thermoelectric and mechanical properties were studied. Compared with Bi2Te3 matrix, Bi2Te3 materials dispersed with nano-SiC show increased Seebeck coefficient, decreased electrical conductivity, and reduced thermal conductivity as well in the measured temperature range of 323–523K. The maximum dimensionless figure of merit (ZT max) was improved from 0.99 for Bi2Te3 sample to 1.04 for 0.1vol% SiC dispersed Bi2Te3 sample at 423K. The Vickers hardness increased linearly from 0.62 to 0.79GPa as 1.0vol% SiC was added. The highest fracture toughness of 1.34MPam1/2 was obtained for 0.1vol% SiC addition, and the highest Young''s modulus of 42.7GPa was obtained for 0.5vol% SiC added sample. [Copyright &y& Elsevier]

Thermoelectric materials can directly convert heat to electricity and vice versa. ZT (= S 2 σ T / κ) is usually used for evaluating the performance of thermoelectric materials. Improving ZT is a challenging task because of the strong interdependence among the Seebeck coefficient (S), electrical conductivity (σ) and thermal conductivity (κ). This review provides a summary of some promising thermoelectric materials in different developing stages with emphasis on the corresponding strategies for thermoelectric performance enhancement. In addition, the number of recent publications on some representative thermoelectric materials is summarized, addressing the current research interests in this field. Thermoelectricity still need intensified scientific efforts to meet the practical demand. • Summarize most promising bulk thermoelectric materials. • Enumerate traditional thermoelectric materials and the corresponding performance enhancing strategies and developing status. • Some emerging and burgeoning materials with outstanding thermoelectric performance are reviewed. [ABSTRACT FROM AUTHOR]

Abstract It is an urgency to find capable lead-free piezoelectric ceramics to show effort towards environmental protection. Bi 0.5 Na 0.5 TiO 3 (BNT)-based piezoelectric ceramics is one of the most promising lead-free systems, for which compositional modification is an efficient way to enhance the piezoelectric performance. In this work, lead-free 0.82(Bi 0.5 Na 0.5)TiO 3 -(0.18- x)BaTiO 3 - x (Bi 0.5 Na 0.5)(Mn 1/3 Nb 2/3)O 3 ceramics were synthesized by a conventional solid state reaction method. Polarization and strain hysteresis loops implies a phase transition from FE (ferroelectric phase) to ER (ergodic relaxor). An electric field induced high strain of 0.28% occurred at x = 0.0275, which was attributed to the coexistence of FE and ER phases. It is considered that our work can help to understand the complex phenomenon observed in BNT-based lead-free system. Highlights • A composition induced phase transition from ferroelectric to relaxor. • The coexistence of ferroelectric and relaxor leads to a high strain. • The strain is enhanced when increasing grain size. • The material is feasible to be developed for practical application. [ABSTRACT FROM AUTHOR]

SnS 0.2 Se 0.8 is a naturally abundant, eco-friendly, and low-cost thermoelectric semiconductor. However, less progress has been achieved for the property enhancement as well as the preparing technologies. P -type SnS 0.2 Se 0.8 and Sn 0.995 Ag 0.005 S 0.2 Se 0.8 polycrystals were synthesized via combining mechanical alloying (MA) and spark plasma sintering (SPS), and their thermoelectric properties were investigated along the direction perpendicular to the SPS–pressurizing direction. The highest figure of merit ( ZT ) of ∼0.76 at 823 K was obtained for undoped SnS 0.2 Se 0.8 sample sintered at 813 K. To further optimize the electrical transport properties, Ag element as an acceptor was doped into SnS 0.2 Se 0.8 . It was found that 0.5 % Ag doping significantly enhanced the power factor from ∼4.12 μW/cm K 2 to ∼5.31 μW/cm K 2 , accompanied by a simultaneous reduction of thermal conductivity at high temperatures. As a result, a high ZT up to ∼1.1 was obtained in Sn 0.995 Ag 0.005 S 0.2 Se 0.8 , which is 45 % higher than that of undoped counterpart. [ABSTRACT FROM AUTHOR]

Ternary copper tin sulfide (Cu–Sn–S) compounds have been investigated for decades as promising candidates of earth-abundant thin film solar cell absorbers. Cu 2 SnS 3 is a representative member of this material system, and is highly expected to be a potential thermoelectric material by the first-principles calculations. In this work, Cu 2 SnS 3 bulk materials were synthesized by the mechanical alloying (MA) combined with spark plasma sintering (SPS), and their crystal structures, electronic transport properties and enhanced thermoelectric performance were systematically investigated. We found that pristine Cu 2 SnS 3 is a p-type thermoelectric material with a relatively high thermopower up to 300 μV/K and low thermal conductivity below 1.0 W/m K above 700 K. It revealed that In doping is an effective means to improve the electrical transport properties, which leads to a figure of merit ( ZT ) of Cu 2 Sn 0.9 In 0.1 S 3 close to 0.6 at the relatively low temperature (773 K). [ABSTRACT FROM AUTHOR]

Bismuth molybdate (Bi 2 Mo 2 O 9 , BMO) has drawn great attention as an excellent catalysis for partial oxidation of light olefins and microwave dielectric materials. Due to its complex crystal structure and intrinsically low thermal conductivity, BMO may be a possible candidate for thermal barrier coating and thermoelectric application. According to our knowledge, however, no related studies on this issue have been reported. In this work, polycrystalline BMO samples with high phase purity and density were synthesized by the solid state reaction method. Various thermophysical properties including thermal expansion coefficient, heat capacity and thermal conductivity were investigated for the first time as far as we know. BMO was found to exhibit a low thermal conductivity of 1 W/mK at room temperature. A close look was taken to the sound speed, Young's modulus and phonon mean free path, providing a detailed interpretation for the origin of this intrinsically low thermal conductivity. [ABSTRACT FROM AUTHOR]

Lead-free p-type AgSn m SbTe m +2 ( m = 2, 4, 10, 18) compound thermo-electric materials were fabricated by a process combining mechanical alloys and spark plasma sintering. The electrical and thermal transport properties of samples with different m values in a wide range were investigated for compositional optimization with the most enhanced thermoelectric performance. It was found that both electrical and thermal conductivity increase with increasing m value, but the Seebeck coefficient shows a maximum at m = 4, resulting in an optimal composition with a relatively high thermoelectric figure of merit up to ZT ≈ 0.8 at 723 K. This work also confirmed that MA–SPS processing could be applied to the synthesis of AgSn m SbTe m +2 compound thermoelectric materials. [ABSTRACT FROM AUTHOR]

BiCuSeO-based oxyselenide compounds show promising thermoelectric properties, but its thermal stability and oxidation behavior are unknown, which were investigated in the present work with a PbTe-based thermoelectric alloy as a comparison. It was revealed that the BiCuSeO polycrystalline materials displayed much better thermal stability in air than the PbTe-based alloys that were severely oxidized at 573 K, resulting in a decreased density and significantly reduced electrical conductivity. Nevertheless, it was found that the BiCuSeO-based thermoelectric materials could not be used in air for a long time as a conventional oxide at high temperatures; apparent decomposition occurred in the BiCuSeO samples when heated at 773 K, although at 573 K the oxidation was limited to the surface accompanied by the formation of bismuth oxide. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanocrystalline n-type Bi2Te3 films are deposited by magnetron sputtering. [•] Pb doping increases the Seebeck coefficient of Bi2Te3 thin films. [•] Pb doping reduces the carrier thermal conductivity of Bi2Te3 thin films. [•] Optimal Pb doping enhances the power factor of Bi2Te3 thin films. [ABSTRACT FROM AUTHOR]