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NaNbO3-based ceramics usually show ferroelectric-like P-E loops at room temperature due to the irreversible transformation of the antiferroelectric orthorhombic phase to ferroelectric orthorhombic phase, which is not conducive to energy storage applications. Our previous work found that incorporating CaHfO3 into NaNbO3 can stabilize its antiferroelectric phase by reducing the tolerance factor (t), as indicated by the appearance of characteristic double P-E loops. Furthermore, a small amount of MnO2 addition effectively regulate the phase structure and tolerance factor of 0.94NaNbO3-0.06CaHfO3 (0.94NN-0.06CH), which can further improve the stability of antiferroelectricity. The XRD and XPS results reveal that the Mn ions preferentially replace A-sites and then B-sites as increasing MnO2. The antiferroelectric orthorhombic phase first increases and then decreases, while the t shows the reversed trend, thus an enhanced antiferroelectricity and the energy storage density Wrec of 1.69 J/cm3 at 240 kV/cm are obtained for 0.94NN-0.06CH-0.5%MnO2(in mass fraction). With the increase of Mn content to 1.0% from 0.5%, the efficiency increases to 81% from 45%, although the energy storage density decreases to 1.31 J/cm3 due to both increased tolerance factor and non-polar phase.

Photocatalytic fixation of nitrogen to ammonia (NH3) is green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N2 and the band position of TiO2 are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO2 hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol gcat-1 h-1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H2O2 treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol gcat-1 h-1 after reducing oxygen vacancies by H2O2 treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol gcat-1 h-1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.

Room-temperature thermoelectric materials provide promising solutions for energy harvesting from the environment, and deliver a maintenance-free power supply for the internet-of-things (IoTs). The currently available Bi2Te3 family discovered in the 1950s, still dominates industrial applications, however, it has serious disadvantages of brittleness and the resource shortage of tellurium (1 × 10−3 ppm in the earth's crust). The novel Mg3Sb2 family has received increasing attention as a promising alternative for room-temperature thermoelectric materials. In this review, the development timeline and fabrication strategies of the Mg3Sb2 family are depicted. Moreover, an insightful comparison between the crystallinity and band structures of Mg3Sb2 and Bi2Te3 is drawn. An outlook is presented to discuss challenges and new paradigms in designing room-temperature thermoelectric materials.

Photocatalytic NO3– reduction in water has been regarded as a promising route due to its high efficiency and green feature. Several limiting factors, such as lack of catalytic sites, insufficient light collection, and spatial charge separation capacity photocatalytic denitrification, still need to be overcome for the practical applications. Herein, an innovative LiNbO3/ZnS heterojunction with a unilateral opening core–shell structure was constructed. ZnS was tightly anchored on the surface of LiNbO3 by modified electrostatic self-assembly method. High nitrate removal rate (98.84%) and N2 selectivity (98.92%) were achieved with a molar ratio of LiNbO3 and ZnS of 1:5 (1:5L-ZS) using formic acid as a hole scavenge. The LiNbO3/ZnS degradation kinetics of NO3– was corresponding to the first-order kinetics equation. The nitrate removal rate and N2 selectivity remained stable after three cycles in such photocatalytic NO3– reduction. The outstanding photocatalyst performance can be ascribed to the improved surface active sites, the well-matched band structure, and the unique core–shell structure. It provides an effective strategy for controllable fabrication of core–shell photocatalyst with strong light-harvesting ability and charge separation efficiency to enhance the removal rate of nitrate in water.

Transition metal carbides are candidates for high-temperature structural ceramics because of their high melting point, high hardness, and high strength. However, one challenge is overcoming their high intrinsic brittleness. In this study, we investigated a new class of (Fe, Mo, W)6C carbides, which have three Wyckoff positions for metallic atoms (16d, 32e, and 48f) and one Wyckoff position for carbon (16c). These different Wyckoff positions provide a great opportunity to optimize the mechanical properties by the partial replacement of atoms at each Wyckoff position to obtain high-entropy carbides. The current results show that the phonon spectra have no imaginary frequency when Fe occupies the 16d or 32e positions, but a soft mode is observed when Fe occupies 48f. (Fe, Mo, W)6C η carbides have a higher fracture toughness compared with those of M3C and MC carbides owing to their low carbon content (14.3 at.%). The mechanical anisotropy of (Fe, Mo, W)6C is weak, which is beneficial for increasing the damage tolerance. The thermal expansion coefficients of the (Fe, Mo, W)6C η carbides are predicted to be approximately (8.5–9.5) × 10−6 K−1 at 1400 K.

Bi2S3-based alloys are considered promising thermoelectric materials due to their large Seebeck coefficient and low lattice thermal conductivity. However, low electrical conductivity usually leads to poor electrical transport properties, which seriously restricts their further application in thermoelectric refrigeration and/or power generation. In this work, Bi2S3 with high electrical transport properties is synthesized hydrothermally via Se and Cl co-doping. The maximum electrical conductivity value of 483 S cm−1 was obtained for the Bi2S2.4Se0.4Cl0.20 sample at room temperature. The significant improvement of electrical conductivity gives rise to a high average power factor of 411 μW m−1 K−2 during the measuring temperature range and a peak value of 456 μW m−1 K−2 at 673 K. Benefiting from the largely improved electrical transport properties, a superior ZT value of approximately 0.66 and ZTave. of 0.36 were obtained for Bi2S2.4Se0.4Cl0.20, and the theoretically calculated conversion efficiency reached 5.7%. The results indicate that Bi2S3 is a promising candidate for thermoelectric applications at medium temperatures.

InGaO3(ZnO)m (m = 1, 2, 3, 4, and 5) ceramics are a series of n-type oxide thermoelectric materials with layered structures and low thermal conductivities. Herein, InGaO3(ZnO)m (m = 1, 2, 3, 4, and 5) ceramics were fabricated by spark plasma sintering (SPS). Two different trends in the thermoelectric properties of the InGaO3(ZnO)m (m = 1, 2, 3, 4, and 5) ceramics were observed depending on the odevity of the m value. The InGaO3(ZnO) sample exhibited a relatively high electrical conductivity and was therefore selected for vacuum annealing to further improve the electrical transport performance. Oxygen vacancy defects were introduced to the matrix during the annealing procedure, which improved the thermoelectric performance. A maximum ZT of 0.45 was obtained at 973 K for the InGaO3(ZnO) sample with a 96 h vacuum annealing treatment, which is 30 times higher than that of the pristine sample.

CuPbBi5S9 compounds have been investigated as gladite for years. However, there have been no significant studies on their physical and chemical properties. This work demonstrates that upon alloying with moderate Cu, Pb, Bi, and S using an appropriate preparation method, quaternary CuPbBi5S9 compounds can exhibit excellent figure of merit ZT within the temperature range 298–723 K. A low average velocity, low Young’s modulus and Debye temperature, and large Gruneisen parameter, determined experimentally, indicate strong lattice anharmonicity in CuPbBi5S9 crystals. Furthermore, density functional theory calculations (local vibration of low-frequency acoustic phonons) justify the low lattice thermal conductivity of CuPbBi5S9 compounds. Because of the low thermal conductivity (0.514 W m−1K−1) and a relatively high power factor (293 μW m−1K−2), a maximum ZT of 0.42 was achieved at 723 K for CuPbBi5S9 prepared by mechanical alloying combined with solid-state melting. Thus, CuPbBi5S9 materials are promising candidates for use as high-performance thermoelectric materials in the intermediate-temperature range.

Nanoparticle-mediated laser-induced breakdown (LIB) can be used for Nanoparticle synthesis, cell nanosurgery and laser-induced breakdown spectroscopy (LIBS). To investigate the photo-thermal conversion of gold nanoparticles during pulsed laser irradiation, the electron-phonon two-temperature model was established in this study. The impact of laser energy density and pulse width on the thermal conversion and morphology change of gold nanorods were investigated and compared with experimental observations. The results show that the melting threshold of gold nanorods under nanosecond laser irradiation is about twenty times that of femtosecond laser irradiation. The mechanisms of nanorod fragmentation are different between fem to and nanosecond laser irradiation: particle melting is more likely to occur in nanosecond laser irradiation, while the Coulomb explosion is highly likely to occur in femtosecond laser irradiation.

As an innovative method that may change the manufacturing landscape in the near future, submerged arc additive manufacturing (SAAM) offers the benefits of flux protection and an inherent intrinsic heat treatment (IHT) for fabricating large-sized, high toughness parts in-situ. In this study, the influence of interlayer temperature on microstructure and mechanical properties of SAAM-processed low-carbon steel were elucidated with a particular focus on the toughening mechanism subjected to the in-situ IHT, which was first time comprehensively analyzed. Our SAAM-processed steel is found toughened in-situ by raising the critical fracture stress (reducing the effective grain size), and yield strength is also slightly lowered in-situ (softening the matrix), at a readily accessible interlayer temperature of ~200 °C for an optimal strength-toughness combination. This allows for the effective suppression of ductile-brittle transition (ductile-brittle transition temperature: ~ − 108 °C). The superior impact toughness (over 300 J at −60 °C) mainly origins from: (i) the pronounced amount of α-Fe (ferrite, BCC) that are intrinsically soft and facilitate plastic deformation, thereby impede the initiation and propagation of cracks; (ii) the fine-grained structure of multiple-recrystallized α-Fe phase and the increase of high-angle grain boundaries that make energy consumption more easily via tortuous crack propagating; (iii) the dispersedly distributed globular cementite structures formed by the decomposition of lamellar pearlite reduce the microcrack nucleation sites and release the strain concentration. The present SAAM method offers a solution for economically manufacturing large engineering components with uniform mechanical properties that exhibit an irreplaceable role in the low-temperature application with moderate strength requirements but extremely high in toughness.

Bi2S3 is composed of inexpensive and environmental friendliness elements, which has received extensive interests and been investigated as a promising mid-temperature thermoelectric material for years. Even pure Bi2S3 possesses a high Seebeck coefficient and low thermal conductivity, its low electrical conductivity leads to a low figure of merit (ZT) value. In this work, Bi2S3 fabricated by solid-state melting combined with spark plasma sintering can significantly enhance the thermoelectric performance via introducing small amounts of Cu and BiCl3. Cu interstitial doping and Cl substitution on S site result in a large increase in electrical conductivity. Additionally, the enhanced phonon scattering is derived from the point defects caused by element doping, the grain boundaries, and the small amount of secondary phase, which leads to the low thermal conductivity. Finally, a high ZT value of 0.7 is obtained at 773 K and reaches a large average ZT of 0.36 in the temperature range from room temperature (RT) to 773 K for the Cu-interstitial-doped and BiCl3-alloyed (Cu0.01Bi2S3 + 0.175 mol% BiCl3) sample. Furthermore, the mechanical properties of the Cu0.01Bi2S3 + 0.175 mol% BiCl3 sample are lower than those of other Bi2S3 samples, which stem from the weak chemical bonding strength.

The large-scale application of lithium sulfur batteries is impeded by their cycling stability and power performance mainly due to the polysulfide shuttle effect and low conductivity of sulfur. Herein, a multifunctional sulfur host of N/S co-doped porous graphene layered matrix (NSPG) is fabricated. High specific surface area of NSPG can guarantee the homogeneous deposition and high utilization of S/Li2S. Moreover, the layered graphene skeleton with abundant crumples can not only construct efficient channels for fast electrolyte ion/electron transfer but also effectively buffer the volume expansion of S during long-time charge/discharge process. DFT calculations verify that the N/S co-doping can promote the redox reaction rate and inhibit the polysulfides shuttle effect through chemical bonding interaction. Benefiting from the above synergistic effects, the NSPG/S electrode exhibits excellent rate performance (646 mAh g−1 at 10C) and outstanding cycle stability (693 mAh g−1 after 500 cycles). Even at a high mass loading of 4.5 mg cm−2, a capacity of 786 mAh g−1 can be retained after 100 cycles. This work might offer a feasible solution for developing sulfur host with multifunctionality and electrocatalytic activity for high-performance lithium sulfur batteries.

Bi0.42Sb1.58Te3 + x wt % Cu1.8S (x = 0, 0.03, 0.05, and 0.1) bulk materials with enhanced thermoelectric and mechanical properties were fabricated by a solid-state reaction and spark plasma sintering. The thermoelectric properties, such as electrical transport properties and thermal conductivity, are highly dependent on the Cu1.8S content. The highest value of ZT obtained for Bi0.42Sb1.58Te3 with 0.05 wt % Cu1.8S is 1.23 at 373 K, and an optimistic average ZT of 1.2 is achieved at temperatures in the range of 323-448 K, which is 34% higher than that of the pristine sample. The highly enhanced ZT of the doped sample is attributed to the increased electrical conductivity and reduced lattice thermal conductivity caused by the effective element doping and the multiscale phonon scattering by quantities of point defects, twin boundaries, and nanopores. Further, the hardness obtained for this sample is 1.02 GPa, which is increased by 16% in comparison with that of the pristine sample. The conversion efficiency of the doped sample is also significantly higher than that of the pristine sample. Therefore, Cu1.8S is considered to be a promising dopant for enhancing the thermoelectric and mechanical properties of Bi-Sb-Te-based thermoelectric materials.

Improving both surface and space utilization of active carbon is crucial for compact supercapacitors. Herein, two activated carbons are prepared through homogeneous activation (HAC) and traditional outside-in activation (OIAC). Compared with OIAC with deep and branched porous structure, HAC shows an interconnected porous structure, leading to higher density, better gravimetric and volumetric capacitances, and improved rate performance. The results demonstrate that interconnected porous structure by homogeneous activation promotes high surface and space utilization as well as robust ion transport kinetics of activated carbon for capacitive energy storage.

Flexible piezoelectric thin films are raising interest in energy harvesting and wearable electronics, although their direct fabrication is challenging in the selection of substrates and thermal processing. In this work, we developed direct fabrication of flexible lead-free (K, Na)NbO3 (KNN)-based piezoelectric films on commercially available metallic foils by sol-gel processing. Stainless steel and platinum foils are selected as flexible substrates because of their good thermal stability, robust flexibility, and cost-efficiency. The sol-gel-processed KNN-based thin films on both of the metallic foils show good flexibility, with the bending radii reaching ±3 mm. The flexible thin films grown on stainless steel and platinum foils present high breakdown electric fields that reach 1760 and 2530 kV/cm, respectively, resulting from the fine-grained dense structure, limited leakage current density, and suppressed mobility of charged carriers. Improved effective piezoelectric coefficient d33, eff* (75.4 pm/V) with a slight decrease after bending was obtained in the flexible thin films on Pt when compared to their rigid counterparts. The flexible lead-free piezoelectric thin films with combined high breakdown electric fields and piezoelectric and energy storage properties may pave the way for integrating KNN-based multifunctional thin films into flexible electronics.

We report a feasible method to realize tunable surface plasmon-polariton (SPP) resonance in organic light-emitting devices (OLEDs) by employing corrugated Ag-Al alloy electrodes. The excited SPP resonance induced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes. With an appropriate composition ratio of the corrugated alloy electrode, the photons trapped in SPP modes are recovered and extracted effectively. The 25% increasement in luminance and 21% enhancement in current efficiency have been achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.

The management of thermal conductivity is of significant scientific interest, particularly for thermal barrier coatings (TBCs). Multifarious strategies have been used to regulate heat transportation, but it is hard to achieve limit thermal conductivity at elevated temperatures. A systematical investigation of weberite (La1-xGdx)3NbO7 was thus performed, and multiphonon scattering mechanisms were introduced to achieve limit thermal conductivity (0.92 W m−1 K−1). Phonon point defect scattering process accounted for thermal conductivity reduction at low temperatures. Additionally, lattice softening strongly contributed to the reduction of high-temperature thermal conductivity, and solid and stiff chemical bonds were beneficial for inhibiting thermal radiative conductivity. A novel strategy was presented to modify thermal transportation property of weberite RE3NbO7 ceramics. Also, the hardness, toughness, and modulus were improved to promote engineering applications of weberite RE3NbO7. This study also illuminates novel paths for thermal management and mechanical properties manipulation of TBCs, thermoelectric materials, and microelectronics.

Ferroelectric perovskite oxides exhibit the bulk photovoltaic effect, which enables an above-bandgap photovoltage, controllable photocurrent response, and higher efficiencies. Herein, the phase structure, ferroelectric, dielectric, light absorption, and photovoltaic properties in (Ba0.95Ca0.05)(Ti0.92Sn0.08-xZrx)O3 (BCTSZx) ceramics were investigated. All BCTSZx samples had good ferroelectric properties along with a narrow band gap (Eg = 2.53–2.60 eV). A large photovoltaic response under AM 1.5 G simulated sunlight was observed in the poled BCTSZ0.06 ceramics, in which the maximum short-circuit current (JSC = 3.66 nA cm−2) as well as the highest transient current (JTC = 32.56 nA cm−2) and photocurrent (JPC = 12.63 nA cm−2) were obtained in 500 μm-thick sample negatively poled at 30 kV cm−1. Our results deepen an understanding of the ferroelectric photovoltaic mechanism of perovskite materials and provide a new material for photovoltaic and multifunctional applications.

Summary CeO2-based nanostructures have recently aroused interest for various applications because of their higher OSC and redox properties, allowing them to facilely switch between the oxidation states of Ce4+ and Ce3+. There are many studies that have been focused on the morphology-dependent catalysis and identification of the true active sites during catalysis reactions. Probing the intrinsic properties of CeO2 nanostructures, including the surface structure and reduction, oxygen vacancy, grain boundary, morphology, and dynamic structure under environmental conditions, is essential in clarifying their physical and chemical properties and expanding their potential applications. In this review, we summarize recent significant achievements in characterizing CeO2 nanostructures and related catalytic phenomena through advanced techniques. Several studies using model CeO2 catalysts have been selected to show the importance of strong metal-support interactions. A deep insight into the active sites in morphologically controllable CeO2 that exposes the highly active facets is expected to guide the design of nanocatalysts.

Thermoelectric materials transfer heat and electrical energy, being useful for power generation or cooling applications. Many of these materials have narrow bandgaps, especially for cooling applications where this property has been seen as particularly important for enhancing the thermoelectric properties. We developed SnSe crystals with a wide bandgap Eg ~ 33 kBT with attractive thermoelectric properties through Pb alloying. The momentum and energy multiband alignment promoted by Pb alloying resulted in an ultra-high power factor ~75 μWcm–1K–2 at 300 K, and a ZTave ~ 1.90. We show that a 31-pair thermoelectric device can produce a power generation efficiency ~4.4% and a cooling ΔTmax ~ 45.7 K. These results demonstrate that wide bandgap compounds can be used for thermoelectric cooling applications.

Nanotechnology refers to technology that studies the performance and usage of materials with a structure size of 0.1 to 100 nanometers. Due to the special size of this material, it determines that ...

With the rapid development of various industries, the machinery manufacturing industry has been constantly carrying out reform and innovation, among which the introduction and use of technology is ...

Piezoelectrics exhibit mechanical strain in response to electrical stimuli and vice versa. A high level of electric-field-induced strain with minimal hysteresis is desired for piezoelectric materials when used as actuators. The past two decades have seen extensive research into lead-free piezoelectrics to replace Pb(Zr,Ti)O3 and compositional engineering has been demonstrated to be an effective method to tailor their functional properties. Doped (K,Na)NbO3 (KNN) compositions with elaborate compositional tuning can exhibit enhanced electromechanical properties. However, a balance between enhanced properties and non-toxicity of the dopants should be considered. In this work, we propose to use microstructural engineering to enhance the properties. Based on phase-field simulations, we propose to take advantage of depolarization energies generated by polar-nonpolar interfaces, to increase the contribution of domain wall motion to electric-field-induced strain. Heterogeneous ferroelectric-paraelectric microstructures were introduced into a KNN ceramic via a two-step sintering process. Their presence was characterized by high-resolution transmission electron microscopy. Enhanced reversible domain wall motion was verified by in situ high-energy X-ray diffraction. Electric-field-induced strain is enhanced by 62% and 200% at 25 °C and 150 °C, respectively. Considering lead-free piezoelectrics also represent an emerging class of biomaterials for medical technology, the non-toxicity and biocompatibility of the investigated compositions are examined by in vitro cell viability assays. Our results demonstrate that microstructural engineering is a promising alternative approach to enhance the electric-field-induced strain of lead-free piezoelectrics while maintaining biocompatibility

Optical imaging has played a vital role in development of biomedicine and image-guided theragnostic. Nevertheless, the clinical translation of optical molecular imaging for deep-tissue visualization is still limited by poor signal-to-background ratio and low penetration depth owing to light scattering and tissue autofluorescence. Hence, to facilitate precise diagnosis and accurate surgery excision in clinical practices, the responsive optical probes (ROPs) are broadly designed for specific reaction with biological analytes or disease biomarkers via chemical/physical interactions for photoacoustic and second near-infrared fluorescence (NIR-II, 900–1700 nm) fluorescence imaging. Herein, the recent advances in the development of ROPs including molecular design principles, activated mechanisms and treatment responses for photoacoustic and NIR-II fluorescence imaging are reviewed. Furthermore, the present challenges and future perspectives of ROPs for deep-tissue imaging are also discussed.

Proteinaceous fibers based on spidroins have attracted widespread attention due to their lightweight and mechanically strong properties. Presently, mechanical modulation is mainly dependent on the ...

Fabrication of nanoparticle-dispersed composites is an effective strategy for enhancing the performance of thermoelectric materials, and in particular SiC nanoparticles have been often used to create composites with Bi2Te3-based applied thermoelectric materials. However, the effect of particle size on the thermoelectric performance is unclear. This work systematically investigated the electrical and thermal properties of a series of (Bi,Sb)2Te3-based nanocomposites containing dispersed SiC nanoparticles of different sizes. It was found that particle size has a significant impact on the electrical properties with smaller SiC nanoparticles giving rise to higher electrical conductivity. Even though the dispersed SiC nanoparticles enhanced the Seebeck coefficient, no apparent dependence of the enhancement on the particle size was observed. It was also found that smaller SiC nanoparticles scatter phonons to some extent while the larger nanoparticles contribute to increased thermal conductivity. Eventually, the highest ZT value of 1.12 was obtained in 30 nm-SiC dispersed sample, corresponding to an increase by 18% from 0.95 for the matrix made from commercial scraps, and then the ZT was further boosted to 1.33 by optimizing the matrix composition and expelling excess Te during the optimized spark plasma sintering process. This work proves that the dispersion of smaller SiC nanoparticles in p-type (Bi,Sb)2Te3 materials is more effective than the dispersion of larger nanoparticles. In addition, it is revealed that additional compositional and/or processing optimization is vital and effective for obtaining further performance enhancement for nanocomposites of SiC nanoparticles dispersed in (Bi,Sb)2Te3.

Extremely low lattice thermal conductivity is always the pursuit of thermoelectric materials research. In this work, we reported an exceptional effect of Ag2S addition in MnTe, an emerging promising mid-temperature thermoelectric material, to enable the realization of minimum lattice thermal conductivity, namely ∼0.4 Wm−1K−1. Such a low lattice thermal conductivity is guaranteed by the incorporation of in-situ formed Ag rich phase (Ag2Te) with ultralow lattice thermal conductivity and further scattering of phonons from the partial doping effects induced point defects and boundaries between various phases. Apart from the dramatically decreased lattice thermal conductivity, the partial doping of Ag and S simultaneously enhance the electrical conductivity, further contributing to enhanced thermoelectric performance. Meanwhile, an inverse sign of Seebeck and Hall coefficient was observed and rationalized by the influence of highly electron-conductive Ag2Te phase. Thanks to the synergetic modulation of electrical and thermal transport properties by in-situ formed composite, a high ZT value of 1.1 was achieved in MnTe based thermoelectric materials, which also demonstrates the importance of compositing approaches to design state-of-the-art thermoelectric materials.

This study investigates rare earth RE3TaO7 ceramics and shows that these materials may be optimal for thermal barrier coatings. ZrO2-Sm3TaO7 ceramics were prepared through a solid-state reaction. X-ray diffusion and structural refinement revealed a phase structure with an ordered orthorhombic phase for the Ccmm space group. The degree of structural disorder increased with increasing ZrO2 content. Gaussian function fitting of the oxygen 1s X-ray photoelectron spectra showed that the Sm3+ and Ta5+ ions were replaced by Zr4+ ions. At high temperatures, 8 mol% ZrO2-Sm3TaO7 has a high thermal expansion coefficient (10.9 × 10−6 K−1). The thermal conductivities of ZrO2-Sm3TaO7 (1.17 − 1.75 W·m−1 K−1) are lower than those of 7–8 wt.% yttria-stabilized zirconia, while those of 2% ZrO2-Sm3TaO7 are the lowest. The oxygen vacancies maintain the charge in equilibrium and enhance phonon scattering while decreasing the thermal conductivity. These results indicate that Sm3TaO7 can be used as a TBC.

We report a detailed analysis of the crystal structure, electronic structure, and thermoelectric (TE) properties of a stoichiometric Mn2CoAl inverse full-Heusler alloy, which has been predicted to ...

The year of 2021 is the 100th anniversary of the first publication of ferroelectric behaviour in Rochelle salt, focussing on its piezoelectric properties. Over the past many decades, people witnessed a great impact of ferroelectricity on our everyday life, where numerous ferroelectric materials have been designed and developed to enable the advancement of diverse applications. Now the driving forces for ferroelectric studies stem from regulations on environment, human health and sustainable society development. This leads to the resurgence of lead-free ferroelectric materials for the expectation of replacing the state-of-the-art lead-based counterparts. The next wave of explorations into ferroelectric materials maybe related to the Internet-of-Things, which requires millions of self-powered sensors and memories. This will promote research on ferroelectrics for sensing, energy harvesting and storage, communication and non-volatile memories, from centimetre scale to micro and nanoscale. This review gives a brief discussion from the materials viewpoint, on the challenges and current status of lead-free ferroelectrics based on prospective applications.

The powder samples of Ca9Sc(PO4)7:xDy3+ white emitting phosphors were prepared via a solid state reaction technique. The Ca9Sc(PO4)7:Dy3+ samples were researched by using the GSAS Rietveld refinement and X-ray diffraction (XRD) methods, and SEM images and elemental maps were recorded. Under 350 nm excitation, the emission spectra of Ca9Sc(PO4)7:xDy3+ samples have two obvious peaks and one weak peak at 484, 572 and 660 nm, corresponding to the characteristic electron transitions of (4F9/2 → 6H15/2, blue), (4F9/2 → 6H13/2, yellow) and (4F9/2 → 6H11/2, red), respectively. The concentration quenching effect, decay lifetime and thermal quenching of the as-synthesized Ca9Sc(PO4)7:Dy3+ samples were researched systematically. The Ca9Sc(PO4)7:0.02Dy3+ phosphor possesses a good thermal stability, of which the emission intensity at 423 K can maintain 79% of the initial value (273 K). In addition, through the study of the chromaticity coordinates of the Ca9Sc(PO4)7:0.02Dy3+ phosphor, it is found that it is located in the white region, and the Commission Internationalede L'Eclairage (CIE) chromaticity coordinates are (0.339, 0.389). The above results show that Ca9Sc(PO4)7:xDy3+ phosphors can be excellent candidate material for applications in NUV-excited white LEDs.

As a kind of ionic fluid, deep-eutectic solvent (DES) has been used not only as a solvent but also as a precursor for carbon preparation in recent years. Herein, porous nitrogen-doped carbon (NC) h...

BiFeO3-BaTiO3 is a promising high-temperature piezoelectric ceramic that possesses both good electromechanical properties and a Curie temperature (TC). Here, the piezoelectric charge constants (d33) and strain coefficients (d*33) of (1 - x)BiFeO3-xBaTiO3 (BF-xBT; 0.20 ≤ x ≤ 0.50) lead-free piezoelectrics were investigated at room temperature. The results showed a maximum d33 of 225 pC/N in the BF-0.30BT ceramic and a maximum d*33 of 405 pm/V in the BF-0.35BT ceramic, with TCs of 503 and 415 °C, respectively. To better understand the performance enhancement mechanisms, a phase diagram was established using the results of XRD, piezoresponse force microscopy, TEM, and electrical property measurements. The superb d33 of the BF-0.30BT ceramic arose because of its location in the optimum point in the morphotropic phase boundary, low oxygen vacancy (VO··) concentration, and domain heterogeneity. The superior d*33 of the BF-0.35BT ceramic was attributed to a weak relaxor behavior between coexisting macrodomains and polar nanoregions. The presented strategy provides guidelines for designing high-temperature BF-BT ceramics for different applications.

A Bi2Te3/Bi2S3@Bi nanocomposite with a network microstructure was successfully synthesized via a hydrothermal method and spark plasma sintering. This composite was constructed from Bi2Te3 nanoparticles and Bi2S3@Bi nanowires, and its network structure is beneficial for obtaining excellent thermoelectric performance. A ZT peak of 1.2 at 450 K was realized for the nanocomposite sample.

Herein, a highly active Mott–Schottky nanocatalyst with tunable Schottky barrier was constructed by embedding Co nanoparticles (NPs) into phosphorus-doped graphitic carbon nitrides (PxCN) for the enhanced dehydrogenation of ammonia-borane (AB). Analyses show that P doping can efficiently decrease the work function of g-C3N4 and elevate the conduction band edge potential; thus, P doping offers a simple approach to tune the Schottky barrier of Co/PxCN by varying the doping amount of P atoms. Upon rationally tuning the Schottky barrier from 0.60 to 0.78 eV, the obtained photocatalyst with the molar composition Co/P3.59CN showed a remarkable TOF (total turnover frequency) value of 67.09 mol H2 per mol metal per min for the dehydrogenation of AB under visible light at 298 K, which, to the best of our knowledge, is one of the highest values reported to date for non-noble metal-based monometallic catalysts and is even comparable to those of some noble metal catalysts. This study opens a new prospect for the rational design and preparation of metal/g-C3N4 nanocatalysts with tunable Schottky barriers and provides a simple way to elevate the catalytic activity of these nanocatalysts.

Cubic phase CsPbX3 nanocrystals (NCs) are promising candidates for optoelectronic applications. However, their chemical stability heavily depends on the dynamic ionic surface. In this work, based on the interdependency of the ligands and the reaction solvent, a protocol is developed for high-quality α-CsPbX3 under ambient conditions. Utilizing this method, the size and full width at half maximum of CsPbX3 NCs can be simply tuned via changing the cationic ligands or reaction solvent, such as CH3Cl, CH2Cl2, or toluene. One remarkable result is the synthesis of cubic CsPbI3 NCs, for which large-scale syntheses have not been reported in the literature except for our method, due to significant phase transition at room temperature. Another result is that we have realized ultrasmall sized CsPbCl3 NCs with emission at 385 nm for the first time. Furthermore, the elimination of reaction solvent (such as ODE, DMSO, DMF) in our protocol reduces the purification-induced surface ligand loss and the irreversible phase transition to a nonfluorescent phase. Our CsPbX3 NCs show near-perfect photoluminescence quantum yield (PL QY) and long-term stability in the presence of moisture. Further characterization demonstrates that all the ligands, whether the initial paired X type or the degenerated hybrid L-X type, remain perfectly passivating on the defect sites throughout.

Transparent conductive electrodes (TCEs) have attracted considerable attentions as one of the essential components in optoelectronic devices. High conductivity, transmittance and flexibility are required for the practical applications of the TCEs in wearable and portable electronics. Here, a simple fabrication process of capillary force-induced printing has been developed to realize highly aligned silver nanowires (AgNWs) film with high flexibility, stretchability and conformability. Ultrathin and skin-attachable OLEDs have been realized based on the aligned AgNWs electrode. This work has proposed a low-cost and fast fabrication strategy to realize highly aligned AgNWs electrode for the flexible and stretchable optoelectronic devices.

Magnesium (Mg) alloys have received an increasing interest in the past two decades for their tremendous application potential. The strength and corrosion resistance levels of common Mg alloys are still relativity low, and especially they are to be improved simultaneously. The addition of rare earth (RE) to Mg alloys is believed to be beneficial for both the strength and corrosion resistance, and some RE-modified traditional Mg alloys have been studied and some new RE-containing Mg alloys have been developed by now. However, further simultaneous improvements in both strength and anti-corrosion require a better understanding of the behavior and mechanism of RE in Mg alloys. In this review, the common influence mechanisms of RE on mechanical and anti-corrosion properties of Mg alloys are summarized, and the latest research progress of RE-containing Mg alloys with simultaneously improved strength and corrosion resistance are introduced. It is demonstrated that the research on high-strength and high corrosion resistant RE-containing Mg alloys is still immature, and some opinions and suggestions are put forward for the synergetic improvement of the strength and corrosion resistance of Mg alloys, so as to contribute to the further development of Mg alloys with higher performance.

It is well known that surface passivation and modification are efficient approaches to improve the photoluminescence and stability of perovskites. Although CsPbBr3 nanocrystals (NCs) could be embedded into a Cs4PbBr6 matrix to enhance the photoluminescence property, the limited stability will hinder their applications. It still remains a challenge to convert CsPbBr3 to Cs4PbBr6 in one step with surface modification by using oxide on a single-particle level. Herein, the process of conversion from CsPbBr3 to Cs4PbBr6/CsPbBr3 microcrystals (MCs) by a ligand-assisted supersaturated recrystallization (LASR) method has been studied. To improve its stability, CsPbBr3 has been successfully converted into monodisperse Cs4PbBr6/CsPbBr3@Ta2O5 core–shell MCs through a facile one-step sol–gel method at room temperature. Compared with Cs4PbBr6/CsPbBr3, Cs4PbBr6/CsPbBr3@Ta2O5 has better light stability and thermal stability. Cs4PbBr6/CsPbBr3@Ta2O5 MCs display great enhancement in photoluminescence quantum yield (PLQY) (up to 94.7%) and photoluminescence lifetime (up to 67.8 ns). Furthermore, the luminous efficiency of the WLED device based on Cs4PbBr6/CsPbBr3@Ta2O5 (31.9 lm W−1) is twice that of the WLED device fabricated by Cs4PbBr6/CsPbBr3 (15.2 lm W−1).

Metal halide perovskites are a new class of promising materials in optoelectronic applications. As the optoelectronic properties of lead halide perovskites are determined largely by their morphology, the morphology of perovskites is crucial for their applications. However, the morphology-controllable synthesis of Cs4PbBr6 perovskites has been scarcely reported so far. Here, zero-dimensional Cs4PbBr6 perovskite microcrystals with tunable size and ultra-uniform morphology were synthesized via a facile precipitation method. The as-prepared Cs4PbBr6 microcrystals possess high photoluminescence quantum yields of up to 98% and excellent stability. The content of ligands plays a dominant role in the solubility of PbBr2 and can compete with Cs+ ions for the surface passivation of Cs4PbBr6 microcrystals, thus modulating the kinetics of the reaction to influence the size and phase of the final products. Meanwhile, the synthesized Cs4PbBr6 microcrystals have outstanding thermal stability compared with CsPbBr3 perovskites. Highly emissive hexagonal Cs4PbBr6 microcrystals with excellent stability were used as phosphors for white light emitting diodes (WLEDs), and the luminous efficiency of the WLED device was determined to be as high as 116.84 lm W−1. This study provides an effective and facile approach to fabricate stable Cs4PbBr6 microcrystals with tunable size and excellent photoluminescence properties.