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Atomic ordering, magnetic properties, and electronic structure of Mn<sub>2</sub>CoGa Heusler alloy
摘要： The magnetic properties and atomic arrangement of Mn2CoGa Heusler alloy were investigated experimentally and by theoretical calculations. The magnetic moment derived from spontaneous magnetization at 5 K was 2.06 μB/f.u. and was close to the integer number of the expected value from theoretical calculation and the Slater–Pauling rule predicted by Galanakis et al. The Curie temperature and L21-B2 order-disorder phase transition temperature were 741 and 1047 K, respectively. Powder neutron diffraction experiment results suggested that the atomic arrangement prefers an L21b-type structure rather than that of Hg2CuTi, being consistent with our previous results of high-angle annular dark-field-scanning transmission electron microscopic observations. The magnetic moments obtained were in good agreement with the theoretical values in the model of the L21b-type structure. The density of states obtained by the first-principles calculation combined with the coherent potential approximation in Mn2CoGa with the L21b-type crystal structure maintained the half-metallic character, even though disordering by Mn and Co atoms was introduced.
关键词： powder neutron diffraction,magnetic moment,Half-metal-type ferromagnets,order-disorder phase transition,atomic ordering,Curie temperature
更新于2025-09-09 09:28:46
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Electron-phonon anharmonicity and low thermal conductivity in phosphorous chalcogenide ferroelectrics
摘要： The dependence of thermal conductivity with temperature has been studied for Sn(Pb)2P2S(Se)6 ferroelectrics-semiconductors, showing an ultra-low (0.5 W/m K) thermal conductivity above 250 K and the possibility to tune it at lower temperatures playing with the dopant concentration. This behavior has been explained taking into account the combination of different physical mechanisms: hopping heat conductivity in a lattice with strong electron-phonon anharmonicity linked to the stereoactivity of tin and lead cations electron lone pairs together with valence fluctuations in P2S(Se)6 groups. Besides, the presence of an incommensurate phase in the more covalent compounds, the location of tricritical points near 250 K and the peculiarities of the chemical bonding have all been correlated with the experimental behavior observed.
关键词： Ferroelectricity,Bonding,Thermal Conductivity,Structure–Property Relationship,Temperature Dependence
更新于2025-09-09 09:28:46
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EFFECT OF TEMPERATURE ON NANOCOMPOSITE OF METAL NANOPARTICLES IN PHOTONIC CRYSTALS
摘要： We theoretically investigate the photonic band gaps in one-dimensional photonic crystals based on nanocomposite of silver nanoparticles. The dielectric permittivity is calculated in accordance with temperature dependence of plasma frequency of silver nanoparticle. The effect of temperature on these structures by incorporating the volume expansion coefficient of nanoparticle is analysed. The behaviors of photonic band gaps with variation of filling factor, radii of nanoparticle and temperature are observed. The evolution of these results leads to designing the desired photonic crystals.
关键词： photonic crystals,nanocomposite,photonic band gaps,temperature dependence,silver nanoparticles
更新于2025-09-09 09:28:46
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A New Method to Prepare Few-Layers of Nanoclusters Decorated Graphene: Nb2O5/Graphene and Its Gas Sensing Properties
摘要： During the last decade, due to its excellent electrical, mechanical and thermal properties of chemically modified graphene has been extensively studied for many applications, such as polymer composites, energy-related materials, biomedical applications and sensors. The aim of this work is to evaluate the gas sensing performance of niobium oxide (Nb2O5) nanoclusters deposited onto few-layers graphene powder by magneton sputtering. Two different samples were prepared by changing electrical power of deposition. The materials were deeply morphologically, structurally and chemically characterized. Finally, they were deposited onto alumina substrates and their sensing properties were investigated vs. different gases, showing good sensing performance vs. ppm concentrations of NO2 at room temperature.
关键词： NO2 detection,room temperature,chemoresistive gas sensors,functionalized graphene
更新于2025-09-09 09:28:46
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Negative-temperature-state relaxation and reservoir-assisted quantum entanglement in double-spin-domain systems
摘要： Spin collective phenomena including superradiance are even today being intensively investigated with experimental tests performed based on state-of-the-art quantum technologies. Such attempts are not only for the simple experimental verification of predictions from the last century, but also as a motivation to explore new applications of spin collective phenomena and the coherent control of the coupling between spin ensembles and reservoirs. In this paper, we investigate the open quantum dynamics of two spin ensembles (double-spin domains) coupled to a common bosonic reservoir. We analyze in detail the dynamics of our collective state and its structure by focusing on both the symmetry and asymmetry of this coupled spin system. We find that when the spin size of one of the double domains is larger than that of the other domain, at the steady state this system exhibits two unusual collective behaviors: the negative-temperature-state relaxation in the smaller spin domain and the reservoir-assisted quantum entanglement between the two domains. These results are the consequence of the asymmetry of this system and the decoherence driven by the common reservoir.
关键词： negative-temperature-state relaxation,spin collective phenomena,bosonic reservoir,superradiance,quantum entanglement,quantum dynamics
更新于2025-09-09 09:28:46
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Multioutputs single-stage gate driver on array with wide temperature operable thin-film-transistor liquid-crystal display for high resolution application
摘要： A hydrogenated amorphous silicon (a‐Si:H) thin‐film transistor (TFT) gate driver with multioutputs (eight outputs per stage) for high reliability, 10.7‐inch automotive display has been proposed. The driver circuit is composed of one SR controller, eight driving TFTs (one stage to eight outputs) with bridging TFTs. The SR controller, which starts up the driving TFTs, could also prevent the noise of gate line for nonworking period. The bridging TFT, using width decreasing which connects between the SR controller and the driving TFT, could produce the floating state which is beneficial to couple the gate voltage, improves the driving ability of output, and reaches consistent rising time in high temperature and low temperature environment. Moreover, 8‐phase clocks with 75% overlapping and dual‐side driving scheme are also used in the circuit design to ensure enough charging time and reduce the loading of each gate line. According to lifetime test results, the proposed gate driver of 720 stages pass the extreme temperature range test (90°C and ?40°C) for simulation, and operates stably over 800 hours at 90°C for measurement. Besides, this design is successfully demonstrated in a 10.7‐inch full HD (1080 × RGB×1920) TFT‐liquid‐crystal display (LCD) panel.
关键词： thin film transistor (TFT),wide temperature,high reliability,gate driver,amorphous silicon (a‐Si)
更新于2025-09-09 09:28:46
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Temperature and pressure induced Raman studies of C 60 oxide
摘要： We present temperature, laser power, and pressure dependent Raman spectral analysis of C60 oxide (C60O) thin films prepared by the photolysis method. The first order temperature, laser power, and pressure coefficients of the Raman frequencies are evaluated and are utilized for evaluating the thermal conductivity of C60O. Its thermal conductivity is found to be 0.7 W m-1 K-1 which is marginally higher than that of bulk C60. Raman frequencies corresponding to C–O and C–C bonds blue-shift with a decrease in temperature which is attributed to the thermal contraction of C60O molecules. The density functional measurements have been performed to optimize C60O structure. The contraction in the C–O bond length has been corroborated with the experimental Raman shifts at different temperatures and is used to evaluate the linear expansion coefficient of C60O. Pressure induced compression and polymerization of C60O clusters are also illustrated. This study highlights the interplay between thermal and mechanical transformations in the C60O cluster which may regulate its thermoelectric properties by tuning the intermolecular interactions.
关键词： pressure dependence,thermoelectric properties,Raman spectroscopy,thermal conductivity,C60 oxide,laser power dependence,temperature dependence
更新于2025-09-09 09:28:46
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Na <sub/>0.5</sub> Bi <sub/>2.5</sub> Nb <sub/>2</sub> O <sub/>9</sub> lead-free piezoelectric ceramics with high Curie temperature derived from sol–gel route
摘要： An Aurivillius phase bismuth layer-structured compound, Na0.5Bi2.5Nb2O9 (NBN), has been prepared by an economical aqueous sol–gel technique. The results indicated that pure NBN nano-particles can be obtained at a low temperature of 650°C and the morphology are platelike with grain sizes of about 40 nm. Using these nano-particles, the dense NBN ceramics were fabricated at 1100°C for 2 h. The Curie temperature Tc and piezoelectric coefficient d33 at room temperature for the present ceramic were found to be 770°C and 11 pC/N, respectively. Thermal annealing studies indicate that the NBN ceramic possesses stable piezoelectric properties, demonstrating it is a promising candidate for high-temperature applications.
关键词： sol–gel,Lead free,bismuth layer-structured,Na0.5Bi2.5Nb2O9,temperature-insensitive
更新于2025-09-09 09:28:46
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Low-temperature preparation of a N-TiO2/macroporous resin photocatalyst to degrade organic pollutants
摘要： Highly active TiO2 photocatalysts prepared at a low temperature are promising reagents to degrade organic pollutants. Moreover, the addition of macroporous resins should overcome the poor adsorption properties of TiO2. Here we prepared N-doped TiO2/macroporous resin composites at low temperatures using a hydrothermal-assisted sol–gel method. The results show that the composites have a spherical appearance, which is controlled by the macroporous resin. The composites exhibit high specific surface areas, and the microstructure can be tuned by the temperature. N can be doped into the TiO2 crystal by substitution of oxygen at a lower temperature. N-doped TiO2 particles are distributed on the surface with a dominant crystal form of anatase. The composite prepared at 200 °C gave the best performance for the photocatalytic degradation of rhodamine B, with removal efficiency of 74.8% following 240-min irradiation.
关键词： Low temperature,Macroporous resin,Rhodamine B,TiO2,Photocatalysis
更新于2025-09-09 09:28:46
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Room-temperature synthesis of Mn2+-doped cesium lead halide perovskite nanocrystals via a transformation doping method
摘要： Currently, Mn2+-doped cesium lead halide perovskite nanocrystals have attracted research interests. Here, we report a novel room-temperature transformation doping method for the synthesis of Mn2+-doped CsPbCl3 and CsPb(Br/Cl)3 nanocrystals. Innovatively, the transformation of Cs4PbX6 (X=Cl, Br) phase which has no excitation emission to CsPbX3 phase which has strong luminescence was used in this mechanism. Simply injecting MnCl2 precursor into Cs4PbX6 solution could result in the full transformation of Cs4PbX6 phase to CsPbX3 phase and Mn2+-doped CsPbCl3 or CsPb(Br/Cl)3 were obtained. The basic idea for the transformation doping method is that MnCl2 can not only drive the transformation of the two structures but also Mn2+ can substitute Pb2+. In this reaction, the concentration of Mn precursor is a key influence factor. Moreover, instead of the ligand of OA, the acetic acid was used in our method. Through the adjustment of the ligand in precursor, not just the photoluminescence quantum yields of as-prepared Mn2+-doped CsPbCl3 nanocrystals were improved from 7.8 to 32.6% (Mn2+-doped CsPb(Br/Cl)3 nanocrystals even could reach to 42.7%), the nanocrystals also retained outstanding stability. We propose a combination of structure transformation and ion doping as a perovskite doping mechanism. Our doping method is a novel strategy for lead halide perovskite nanocrystals doping project and it could provide more possibilities in the future.
关键词： photoluminescence quantum yields,Cs4PbX6,Mn2+-doped cesium lead halide perovskite nanocrystals,CsPbX3,room-temperature transformation doping method
更新于2025-09-09 09:28:46