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The upregulation of programmed death-ligand 1 (PD-L1) and epidermal growth factor receptor 2 (HER2) may play a role in gastric adenocarcinoma (GAC).To study PD-L1 and HER-2 expression and prognosis in GAC.PD-L1 and HER2 expression was determined in tumor tissues of 75 patients with GAC. The correlations between PD-L1, HER2 expression, and clinicopathological factors were analyzed.The positive expression rate for PD-L1 was 57.3% (43/75) and the HER2 over-expression rate was 17.3% (13/75). PD-L1 expression negatively correlated with the grade of GAC differentiation (r =-0.26, P0.05). Approximately 85% of HER2-positive GACs were found to be PD-L1-positive and PD-L1 expression positively correlated with HER2 overexpression. The TNM stage and combined HER2 and PD-L1 expression were independent prognostic factors affecting the survival of patients with GAC. The median overall survival and recurrence-free survival of groups I (HER2 overexpression and PD-L1 positive), II (HER2 overexpression and PD-L1 negative), III (No HER2 overexpression and PD-L1 positive) and IV (No HER2 overexpression and PD-L1 negative) were (47 (17-77), 15 (0-44), 81 (62-101), and 78 (60-98) months, respectively.PD-L1 expression is upregulated in more than half of patients with GAC. Anti-PD-L1 treatment combined with anti-HER2 therapy may benefit patients with locally advanced GAC with HER2 overexpression.

We report comprehensive transport, electron microscopy and Raman spectroscopy studies on the transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33T. Through the electron diffraction patterns, the stable room temperature phase is identified as a 3×3×2 modulated superstructure based on Nowotny hexagonal structure. The superlattice spots of Transmission electron microscopy and Scanning tunneling microscopy clearly show the structural transitions from the room temperature Commensurate Ⅰ (C-Ⅰ) phase to the low temperature Commensurate Ⅱ (C-Ⅱ) phase. All the results can be understood in term of charge density wave (CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.

Understanding the origin of intrinsic lattice thermal conductivity in crystalline solids is critical to research fields ranging from thermoelectric materials to thermal barrier coatings. This work ...

NbCoSb, nominally a 19-electron half-Heusler (19-HH) compound, is one of the emerging novel thermoelectric (TE) materials and has attracted much attention in recent years. By introducing a large am...

Summary Aliovalent defects are extremely effective in manipulating charge transport and atomic vibrational properties for thermoelectric enhancements. Electronic performance of thermoelectrics is optimized at a reduced Fermi level of ∼0.3, which causes the optimal carrier concentration (nopt) to be strongly temperature dependent. This motivates a dynamic doping approach for electronic enhancements through an increase with temperature of solubility of aliovalent dopants. In addition, the defects could simultaneously act as scattering sources of phonons for reducing the lattice thermal conductivity. These effects are illustrated in this work by the temperature-dependent excess Cu solubility in n-PbTe0.75Se0.25 thermoelectrics, in which both carriers and dislocations are induced for regulating the electronic and phononic transport properties for a realization of an extraordinary thermoelectric figure of merit. The resultant defect structures and temperature gradient doping effects (for aliovalent solutes) could in principle open extra possibilities for optimizing charge and phonon transport properties in thermoelectrics.

Whether the atomic arrangement has a long-range order bifurcates solid-state matter into two major categories: crystalline and amorphous, between which lies a short-range order, a frontier research topic of fundamental and application implications. To date, it is still challenging to extract the details of short-range order from the corresponding diffuse diffraction pattern due to the phase problem. Here, we employed the high-angle annular dark field (HAADF) imaging technique to pinpoint the short-range order encoded in the one-of-a-kind diffuse the diffraction bands of defective half-Heusler Nb0.8CoSb. Utilizing a protocol based on two limiting cases, we found that the native Nb vacancies up to 20% are dominantly displacive short-range ordered yet spatially correlated. To the best of our knowledge, this is the first time that a dominantly displacive short-range order is reported at the atomic scale. These results are vital for an in-depth understanding and engineering of the thermodynamics and transport properties of the materials with abundant native defects, including but not limited to defective half-Heusler compounds.

Defect engineering is an effective route to improve the performance of thermoelectric materials, including Sb doped PbSe, but the formation mechanism of defects remains unclear. In the thermoelectric material Pb1−xSb2x/3Se (0 < x ≤ 0.07), a large number of dislocations have been reported, and they enhance intermediate-frequency phonon scattering, thereby improving the zT value. However, the microstructural origin of dislocations remains unclear. In this paper, via a combination of atomic resolution scanning transmission electron microscopy and density functional theory, we successfully revealed the microstructure of Pb1−xSb2x/3Se (x = 0–0.07) for in-depth understanding of the formation mechanism of dislocations. Plenty of zinc blende (ZB) nanostructures are found in the PbSe matrix with a rock salt (RS) structure, and the theoretical calculations confirm its viability from the point of view of formation energy. A similar ZB structure is identified in the dislocation cores of Sb-doped materials as well, and thus the formation mechanism of dislocations is discussed for this PbSe system. This result provides important guidance to understand the structural evolution in compounds with a RS structure, especially in high-performance lead chalcogenide thermoelectric materials.

A high conduction band degeneracy (Nv = 6) leads to an extraordinary figure of merit (zT) in n-type Mg3Sb2 thermoelectrics, while the p-type ones show a much inferior zT due to its lower Nv of only 1 owing to the large energy offset (ΔE ∼ 0.4 eV) between the two valence bands. The derivatives of Mg3Sb2, ternary AB2C2 (A = Eu, Yb, Ca, Sr, Ba; B = Mg, Zn, Cd; C = Sb, Bi) Zintls, show a similar valence band structure but with a much smaller ΔE of

Advanced functional materials 10(47), 2209980 (2022). doi:10.1002/adfm.202209980, Published by Wiley-VCH, Weinheim

Lithium-sulfur (Li-S) batteries have attracted widespread attention due to their high theoretical energy density. However, their practical application is still hindered by the shuttle effect and the sluggish conversion of lithium polysulfides (LiPSs). Herein, monodisperse molybdenum (Mo) nanoparticles embedded onto nitrogen-doped graphene (Mo@N-G) were developed and used as a highly efficient electrocatalyst to enhance LiPS conversion. The weight ratio of the electrocatalyst in the catalyst/sulfur cathode is only 9%. The unfilled d orbitals of oxidized Mo can attract the electrons of LiPS anions and form Mo–S bonds during the electrochemical process, thus facilitating fast conversion of LiPSs. Li-S batteries based on the Mo@N-G/S cathode can exhibit excellent rate performance, large capacity, and superior cycling stability. Moreover, Mo@N-G also plays an important role in room-temperature quasi-solid-state Li-S batteries. These interesting findings suggest the great potential of Mo nanoparticles in building high-performance Li-S batteries.

Summary Lattice vibrations in crystalline materials generate phonons as heat carriers for heat conduction, and the phonon dispersion (energy versus momentum) is fundamentally determined by the mass of lattice vibrators (atoms) and the interaction force between atoms. A significant manipulation of lattice thermal conductivity through a change in atomic mass usually requires a large variation in chemical composition, which is not always valid thermodynamically or may risk the resultant detriment of other functionalities (e.g., carrier mobility). Here we show a strategy of alternatively manipulating the interaction force between atoms through lattice strains without changing the composition, for remarkably reducing the lattice thermal conductivity without reducing carrier mobility, in Na0.03Eu0.03Sn0.02Pb0.92Te with stable lattice dislocations. This successfully leads to an extraordinarily high thermoelectric figure of merit, with the help of valence band convergence. This work offers both insights and solutions on lattice strain engineering for reducing lattice thermal conductivity, thus advancing thermoelectrics.

Crystalline solids are characterized by periodic structures, resulting in a diverse assortment of crystal structures that exhibit a wide variety of properties. Here we report short-range order, which results in characteristic diffuse bands in electron diffraction patterns, in a series of defective 19-electron half-Heusler compounds for the first time. The co-existence of the vacancy-related short-range order and the crystalline long-range periodic structure makes these defective half-Heusler compounds promising thermoelectric materials with low thermal conductivity and high electrical conductivity simultaneously. This new finding provides important insights into the intrinsic nature of defective HH compounds, and also proposes a possible strategy for tuning the degree of ordering to offer great potential for further improvement of thermoelectrics.

Controlling lattice vibrations to obtain intrinsic low thermal conductivity play a critical role in thermal management of electronic and photonic devices, energy converters, and thermal insulation, which necessitates exploring new compounds and a thorough understanding of their chemical structure, bonding, and lattice dynamics. Herein, a new chalcogenide, Ga

© 2020 Elsevier B.V. Molten salts are a unique type of electrolyte enabling high-temperature electrochemical energy storage (EES) with unmatched reversible electrode kinetics and high ion-conductivities, and hence impressive storage capacity and power capability. However, their high tendency to evaporate and flow at high temperatures challenges the design and fabrication of the respective EES devices in terms of manufacturing cost and cycling durability. On the other hand, most of these EES devices require lithium-containing molten salts as the electrolyte to enhance performances, which not only increases the cost but also demands a share of the already limited lithium resources. Here we report a novel quasi-solid-state (QSS) electrolyte, consisting of the molten eutectic mixture of Na2CO3-K2CO3 and nanoparticles of yttrium stabilized zirconia (YSZ) in a mass ratio of 1:1. The QSS electrolyte has relatively lower volatility in comparison with the pristine molten Na2CO3-K2CO3 eutectic, and therefore significantly suppresses the evaporation of molten salts, thanks to a strong interaction at the interface between molten salt and YSZ nanoparticles at high temperatures. The QSS electrolyte was used to construct an iron-air battery that performed excellently in charge-discharge cycling with high columbic and energy efficiencies. We also propose and confirm a redox mechanism at the three-phase interlines in the negative electrode. These findings can help establish a simpler and more efficient approach to designing low-cost and high-performance molten salt metal-air batteries with high stability and safety.

Defect engineering is an effective route to improve the performance of thermoelectric materials, including Sb doped PbSe, but the formation mechanism of defects remains unclear. In the thermoelectric material Pb1-xSb2x/3Se (0x ≤ 0.07), a large number of dislocations have been reported, and they enhance intermediate-frequency phonon scattering, thereby improving the zT value. However, the microstructural origin of dislocations remains unclear. In this paper, via a combination of atomic resolution scanning transmission electron microscopy and density functional theory, we successfully revealed the microstructure of Pb1-xSb2x/3Se (x = 0-0.07) for in-depth understanding of the formation mechanism of dislocations. Plenty of zinc blende (ZB) nanostructures are found in the PbSe matrix with a rock salt (RS) structure, and the theoretical calculations confirm its viability from the point of view of formation energy. A similar ZB structure is identified in the dislocation cores of Sb-doped materials as well, and thus the formation mechanism of dislocations is discussed for this PbSe system. This result provides important guidance to understand the structural evolution in compounds with a RS structure, especially in high-performance lead chalcogenide thermoelectric materials.

Whether the atomic arrangement has a long-range order bifurcates solid-state matter into two major categories: crystalline and amorphous, between which lies a short-range order, a frontier research topic of fundamental and application implications. To date, it is still challenging to extract the details of short-range order from the corresponding diffuse diffraction pattern due to the phase problem. Here, we employed the high-angle annular dark field (HAADF) imaging technique to pinpoint the short-range order encoded in the one-of-a-kind diffuse the diffraction bands of defective half-Heusler Nb0.8CoSb. Utilizing a protocol based on two limiting cases, we found that the native Nb vacancies up to 20% are dominantly displacive short-range ordered yet spatially correlated. To the best of our knowledge, this is the first time that a dominantly displacive short-range order is reported at the atomic scale. These results are vital for an in-depth understanding and engineering of the thermodynamics and transport properties of the materials with abundant native defects, including but not limited to defective half-Heusler compounds.

In‐grain dislocation‐induced lattice strain fluctuations are recently revealed as an effective avenue for minimizing the lattice thermal conductivity. This effect could be integratable with electronic enhancements such as by band convergence, for a great advancement in thermoelectric performance. This motivates the current work to focus on the thermoelectric enhancements of p‐type PbTe alloys, where monotelluride‐alloying and Na‐doping are used for a simultaneous manipulation on both dislocation and band structures. As confirmed by synchrotron X‐ray diffractions and Raman measurements, the resultant dense in‐grain dislocations induce lattice strain fluctuations for broadening the phonon dispersion, leading to an exceptionally low lattice thermal conductivity of ≈0. 4 W m‐K−1. Band structure calculations reveal the convergence of valence bands due to monotelluride‐alloying. Eventually, the integration of both electronic and thermal improvements lead to a realization of an extraordinary figure of merit zT of ≈2.5 in Na0.03Eu0.03Cd0.03Pb0.91Te alloy at 850 K., Simultaneous manipulation of in‐grain dislocations for lattice thermal conductivity reduction and band convergence for electronic enhancement leads to a realization of an extraordinary thermoelectric figure of merit in p‐PbTe alloys.

Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics. Alloying with monotellurides has been known to be an effective approach for converging the valence bands of PbTe for electronic improvements, while the lattice thermal conductivity of the materials remains available room for being further reduced. It is recently revealed that the broadening of phonon dispersion measures the strength of phonon scattering, and lattice dislocations are particularly effective sources for such broadening through lattice strain fluctuations. In this work, a fine control of MnTe and EuTe alloying enables a significant increase in density of electron states near the valence band edge of PbTe due to involvement of multiple transporting bands, while the creation of dense in-grain dislocations leads to an effective broadening in phonon dispersion for reduced phonon lifetime due to the large strain fluctuations of dislocations as confirmed by synchrotron X-ray diffraction. The synergy of both electronic and thermal improvements successfully leads the average thermoelectric figure of merit to be higher than that ever reported for p-type PbTe at working temperatures.

Here we find the peculiar behavior of Cu ions in the PbSe–Cu system increases its thermoelectric performance. For the electrical transport, a dynamic doping effect is achieved because more Cu ions enter into the PbSe lattice and provide extra charge carriers as the temperature increases, which guarantees an optimized carrier concentration over a wide temperature range. For the thermal transport, the presence of Cu2Se nanoprecipitates and dislocations at a low temperature range as well as the vibration of Cu atoms around the interstitial sites of PbSe at high temperatures result in hierarchical phonon scattering and a significantly reduced lattice thermal conductivity over the whole temperature range. As a result, a peak thermoelectric material figure of merit zT of up to 1.45 and a thermoelectric device figure of merit ZT close to unity are obtained for the sample with 0.375 at% Cu. Furthermore, enhanced thermoelectric properties are also realized for the Cu-intercalated PbS, implying that the temperature-driven dynamic behavior of Cu ions in a rigid lattice can serve as a general strategy to optimize the thermoelectric performance of IV–VI compounds.

Mg3Sb2-based Zintl phase compounds have attracted considerable attention as promising thermoelectric materials in recent years. Mg defects are generally thought to play an important role in the n-type conduction of Mg3Sb2, and obtaining atomic occupancy of Mg and Sb is important for understanding the relationship of atomic defects and transport properties. However, the high angle annular dark-field (HAADF) and annular bright-field (ABF) in scanning transmission electron microscopy (STEM), which were commonly used to reveal the atomic information of other thermoelectric materials, failed to visualize the Mg atoms of Mg3Sb2, giving an illusion of the disappearance of Mg. In this work, the advanced integrated differential phase contrast (iDPC) technique is used, which clearly visualize the Mg and Sb atoms simultaneously in Mg3Sb2 single crystal. We found that Mg and Sb occupancy the real lattice sites without observing the interstitial Mg atoms. Our results highlight the importance of the iDPC technique in revealing the accurate atomic occupancy of light-element-based thermoelectrics, which will pave the way for understanding the microstructure-properties relationship.

GeSe is a IV-VI semiconductor, like the excellent thermoelectric materials PbTe and SnSe. Orthorhombic GeSe has been predicted theoretically to have good thermoelectric performance but is difficult to dope experimentally. Like PbTe, rhombohedral GeTe has a multivalley band structure, which is ideal for thermoelectrics and also promotes the formation of Ge vacancies to provide enough carriers for electrical transport. Herein, we investigate the thermoelectric properties of GeSe alloyed with AgSbSe2, which stabilizes a new rhombohedral structure with higher symmetry that leads to a multivalley Fermi surface and a dramatic increase in carrier concentration. The zT of GeAg0.2Sb0.2Se1.4 reaches 0.86 at 710 K, which is 18 times higher than that of pristine GeSe and over four times higher than doped orthorhombic GeSe. Our results open a new avenue towards developing novel thermoelectric materials via crystal phase engineering using a strategy of entropy stabilization of high symmetry alloys.

Superconducting films are fascinating due to their tunability associated with the interfacial effects. Here we report the superconductivity of single-crystalline $\mathrm{LaS}{\mathrm{i}}_{2}(112)$ films epitaxially grown on Si(111) substrates, which exhibit the superconducting transition temperature $({T}_{c})$ of 3.2 K in films thicker than 21 monolayers (ML) in the strong-coupling regime. At the interface, the $\mathrm{LaS}{\mathrm{i}}_{2}$ films bear the tensile strain, leading to the formation of thickness-dependent stripes. The local superconducting gap varies in real space in accordance with the stripes. In some areas with the thickness of 10--21 ML the superconductivity is enhanced, while in films thinner than 10 ML the superconductivity is suppressed due to the suppression of electronic states at the Fermi level. Our work provides insights into the interfacial effects on the superconductivity of epitaxial compound films from both lattice and electronic aspects.

Magnetic skyrmions, topological-chiral spin textures, have potential applications in next-generation high-density and energy-efficient spintronic devices for information storage and logic technologies. Tailoring the detailed spin textures of skyrmions is of pivotal importance for tuning skyrmion dynamics, which is one of the key factors for the design of skyrmionic devices. Here, the direct observation of parallel aligned elliptical magnetic skyrmions in Pt/Co/Ta multilayers with an oblique-angle deposited Co layer is reported. Domain wall velocity and spin-orbit-torque-induced out-of-plane effective field analysis demonstrate that the formation of unusual elliptical skyrmions is correlated to the anisotropic effective perpendicular magnetic anisotropy energy density (Keff u ) and Dzyaloshinskii-Moriya interaction (DMI) in the film plane. Structural analysis and first-principles calculations further show that the anisotropic Keff u and DMI originate from the interfacial anisotropic strain introduced by the oblique-angle deposition. The work provides a method to tune the spin textures of skyrmions in magnetic multilayers and, thereby, a new degree of freedom for the design of skyrmionic devices.

Manipulating topotactic phase transformations via orderly ion transfer in complex oxides ABOx is ubiquitous in advanced applications such as ionotronics, ion-batteries and catalysts. Most of such ion-mediated transformations are accomplished by the transfer of oxygen or A-site ions. However, implementing the transformation via the transfer of B-site ions, despite the great challenge to overcome a large cohesive energy, has unique advantage since they host most functional properties of materials. Here, we present a tri-state phase transformation from perovskite (P) to brownmillerite (BM) and to single-layered perovskite (SL) structure via the concerted migration of oxygen and B-site Co-ions in La0.7Sr0.3CoO3 thin films. Ac-STEM, XPS, XAS, PNR, magnetic and electric measurements demonstrated that presented B-site Co-cation transfer is along the CoO4 tetrahedral sub-layer of the BM film, which leads to the reconfiguration of 3d-electrons and spin state in remanent Co ions and causes tremendous changes in magnetic and electric properties: from canted-antiferromagnetic insulator in BM phase to ferromagnetic insulator in SL phase. First-principles calculations revealed that the La3+-doping at A-site largely reduces the cohesive energy of Co-ions in CoO4 and destabilize the CoO4 tetrahedron of BM phase, which explains the formation of Co-ions transfer channel in the CoO4 tetrahedral sub-layer. The present study highlights the effectiveness of regulating topotactic transformation via B-site ions transfer and provides a new pathway for manipulating the topotactic transformation with diverse functionalities.

Compared with widely studied 18-electron half-Heusler (HH) thermoelectric (TE) materials, cation-deficient 19-electron HH compounds have also been recently demonstrated to possess excellent TE performance, exhibiting high potential for TE application. Here, a new defective 19-electron HH compound Ti1-xPtSb is developed with high density-of-state effective mass and low lattice thermal conductivity. The former results from the band degeneracy and high band effective mass, and the latter results from the enhanced phonon scattering by substantial intrinsic Ti vacancies. The optimized carrier concentration, combined with the low lattice thermal conductivity, contributes to a maximum zT of 0.7 in pure-phase Ti1-xPtSb (x = 0.14–0.18) samples, which is about 50% higher than that of the nominal TiPtSb sample, indicating that n-type Ti1-xPtSb HH compounds are promising TE materials.

Perovskite manganite Ca

Perovskite manganite Ca0.9R0.1MnO3−δ (R = Dy, Yb) ceramics have been synthesized by a traditional solid-state reaction with multicalcination processes. A heterogeneous microstructure including large and small micrometer-sized grains, coherent interfaces, and oxygen defects has been formed with optimized calcination time. The carrier concentration of the third-calcined samples is enhanced approximately 3 times compared with those synthesized through conventional methods. Thus, the electrical resistivity of the third-calcined Ca0.9R0.1MnO3−δ (R = Dy, Yb) ceramic samples obviously decreases, leading to a higher power factor. Additionally, the thermal conductivity is also reduced by multiscale scattering of the heterogeneous structure. The lowest lattice thermal conductivities of Dy- or Yb-doped samples are 1.24 and 1.22 W m–1 K–1, respectively. Thus, the high thermoelectric performance for Ca0.9R0.1MnO3−δ (R = Dy, Yb) has been achieved by the multicalcination process. The highest figure of merit is almost 30% higher than that of the first-calcined samples. Therefore, a heterogeneous microstructure formed by optimized multicalcination can effectively optimize the thermoelectric performance of oxides., The work is financially supported by the National Basic Research Program of China (2013CB632506), the Natural Science Fund of China under Grants 51501105, 51672159, and 51611540342, the Young Scholars Program of Shandong University under Grant 2015WLJH21, the China Postdoctoral Science Foundation under Grants 2015M580588 and 2016T90631, the Postdoctoral Innovation Foundation of Shandong Province under Grant 201603027, the Fundamental Research Funds of Shandong University under Grant 2015TB019, and the Foundation of the State Key Laboratory of Metastable Materials Science and Technology under Grant 201703.

SnTe is a p-type thermoelectric material that is isostructural with PbTe, for which it is a potential environmentally friendly replacement. By doping the SnTe lattice with In, the thermal conductivity of SnTe can be significantly reduced and the thermoelectric conversion efficiency improved. A large number of precipitates were present in the In-doped SnTe samples; based on atomic-resolution high-angle annular dark-field images and electron energy loss spectra, these precipitates were identified as the zinc-blende phase of In2Te3. Through geometry phase analysis, a new phonon scattering mechanism is discussed.