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Optical investigation of Er3+ and Er3+/Yb3+ doped zinc-tellurite glass for solid-state lighting and optical thermometry
摘要： Er3+ and Er3+/Yb3+ doped zinc tellurite (ZnO/TeO2) glasses were prepared using melt quenching technique. Spectroscopic properties of the glasses were studied by absorption spectroscopy, luminescence spectroscopy, and color chromaticity coordinates (CIE-1931) measurements. Upconverted-emission intensities and the CIE-1931 coordinates were strongly affected by the presence of Yb3+ ion, as well as the excitation power density of 975 nm laser light. Effect of temperature on green upconverted-emissions from two thermally coupled 2H11/2 and 4S3/2 levels of Er3+ ions were measured and fluorescence intensity ratio technique was applied to investigate the temperature sensing properties. High sensitivity and short response time properties make ZnO/TeO2 glasses a very good candidate for non-contact optical temperature sensor applications. The maximum sensitivity of the glasses doped with Er3+ and Er3+/Yb3+ were found to be 72×10-4 K-1 and 120×10-4 K-1 at 429 K, respectively which are much higher than previously reported temperature sensors based on Er3+ ion doped materials. Hence, Er3+/Yb3+ doped zinc-tellurite glass can be more suitable than that of doped with Er3+ ions only for color tunable solid-state lighting and non-contact optical thermometry applications.
关键词： Solid-state lighting,non-contact optical thermometry,fluorescence intensity ratio (FIR),zinc-tellurite glass,upconversion
更新于2025-09-09 09:28:46
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Applied Nanophotonics || Lighting with nanostructures
摘要： This chapter considers application of various nanostructures in lighting devices and components. It includes an introduction to photometry and color perception by humans, and discussion of colloidal quantum dots as spectral converters in display devices and lighting sources; advances in development of colloidal quantum dot light-emitting diodes (LEDs); epitaxial quantum well structures as the core technology in solid-state lighting; the potential for metal nanostructures to improve efficiency of light sources; and the outlook for challenging issues in this field. The new trends in eye-friendly customized lighting and the lighting adapted to human biorhythms are covered, and possible application of residential lighting systems for wireless optical communication (Li-Fi) are discussed.
关键词： colloidal quantum dots,metal nanostructures,nanostructures,LEDs,Li-Fi,solid-state lighting,lighting devices
更新于2025-09-09 09:28:46
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High-frequency absorption properties of gallium weakly doped barium hexaferrites
摘要： The BaFe12-xGaxO19 (x < 1.2) hexaferrites were synthesised by usual ceramics technology. The Bi2O3 additive in the amount of 3 wt% was applied. The features of crystal structure and unit cell parameters were re?ned using powder X-ray di?raction at 300 K. It is shown that with the substitution level increase the parameters of unit cell monotonically decrease. The magnetisation and susceptibility versus temperature and ?eld for these solid solutions were investigated by the vibration magnetometry method. The main magnetic concentration dependence is shown that with the substitution level the magnetic parameters increase monotonically decrease. The microwave properties of the samples including the external magnetic bias ?eld are also investigated at 300 K. It is shown that with the increase of Ga3+ concentration from x = 0.1 to x = 0.6 the frequency value of natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With the increase in Ga3+ concentration, the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time, the peak amplitude of the resonant curve changes slightly. The frequency shift of NFR in the external magnetic bias ?eld takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material e?ectively absorbing the high-frequency EMR.
关键词： crystal structure,doped hexaferrites,magnetic and absorption measurements,Solid-state reactions
更新于2025-09-09 09:28:46
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Investigation of Structure and Dynamics in a Photochromic Molecular Crystal by NMR Crystallography
摘要： A photochromic anil, N-(3,5-di-t-butylsalicylidene)-4-amino-pyridine, has been studied by single-crystal X-ray diffraction, multinuclear magic-angle spinning NMR and first-principles density functional theory (DFT) calculations. Interpretation of the solid-state NMR data on the basis of calculated chemical shifts confirms the structure is primarily composed of molecules in the ground-state enol tautomer, while thermally-activated cis-keto and photoisomerised trans-keto states exist as low-level defects with populations that are too low to detect experimentally. Variable temperature 13C NMR data reveals evidence for solid-state dynamics which is found to be associated with fast rotational motion of t-butyl groups and 180° flips of the pyridine ring, contrasting the time-averaged structure obtained by X-ray diffraction. Comparison of calculated chemical shifts for the full crystal structure and an isolated molecule also reveals evidence for an intermolecular hydrogen-bond involving the pyridine ring and an adjacent imine carbon which facilitates the flipping motion. The DFT calculations also reveal that the molecular conformation in the crystal structure is very close to the energetic minimum for an isolated molecule, indicating that the ring dynamics arise as a result of considerable steric freedom of the pyridine ring and which also allows the molecule to adopt a favourable conformation for photochromism.
关键词： NMR crystallography,photochromic,anil,solid-state NMR,DFT calculations,molecular dynamics
更新于2025-09-09 09:28:46
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Silicide phase formation by Mg deposition on amorphous Si. Ab initio calculations, growth process and thermal stability
摘要： Formation of magnesium silicides on amorphous silicon by deposition of Mg at room temperature is studied by electron energy loss spectroscopy, differential reflectance spectroscopy and high resolution transmission electron microscopy. Optimal crystal structures of Mg silicides under high pressure are found by ab initio DFT calculations. These structures are related to the particular minima of enthalpy. Dielectric functions are calculated for these structures. The transitions from the cubic phase c-Mg2Si to orthorhombic o-Mg2Si at 5.6 GPa and then from o-Mg2Si to hexagonal h-Mg2Si at 22.3 GPa are predicted using the USPEX code. The experimental spectra and the data obtained from the calculated dielectric functions are mutually consistent. Optical reflectance is suitable for monitoring the growth and transformations of the phases during experiments. During Mg deposition onto amorphous Si, the o-Mg2Si phase forms first, then the c-Mg2Si phase grows upon it. The observed sequence of phase formation is related with the compression stress arising in the depth of the Mg-Si mixture.
关键词： optical reflection spectroscopy,electron energy loss spectroscopy,solid state reactions,thin films,high resolution transmission electron spectroscopy,ab initio calculations
更新于2025-09-09 09:28:46
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Synthesis and Characteristics of New Organic Red Emissive Material Based on Phenanthro[9,10-d]imidazole
摘要： Red emission is one of the three primary colors that are essential for the realization of full-color displays and solid-state lightings. High solid-state efficiency is a crucial factor for the applications in organic light emitting diodes (OLEDs). In this work, two new donor-acceptor-donor type phenanthro[9,10-d]imidazole (PIM) -based derivatives, (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)acrylonitrile) (PIDSB) and 2,3-bis(4'-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)-[1,1'-biphenyl]-4-yl)fumaronitrile (PIDPh), are designed and synthesized. Both of them possess high thermal stabilities. PIDPh shows typical characteristics of aggregation-induced emission enhancement, while PIDSB displays aggregation-caused quenching effect. They both exhibit much red-shifted emissions compared with PIM owing to intramolecular charge transfer. In film state, the emission peaks of PIDSB and PIDPh locate at 538 nm and 605 nm with high photoluminescent quantum yields of 63.82% and 41.26%, respectively. The non-doped OLED using PIDPh as the active layer shows the maximum external quantum efficiency of 2.06% with a very low efficiency roll-off, and exhibits the electroluminescent peak at 640 nm with a Commission Internationale de l'éclairage coordinate of (0.617,0.396), meeting well with the criteria of red OLEDs.
关键词： red emissive material,high solid-state fluorescent efficiency,OLED,Phenanthro[9,10-d]imidazole,low efficiency roll-off
更新于2025-09-09 09:28:46
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Sintering evaluation of doped lanthanum gallate based on thermodilatometry
摘要： The sintering behavior of La0.9Sr0.1Ga0.8Mg0.2O3-δ oxide-ion conductor was systematically investigated by thermodilatometry. The shrinkage data obtained with heating rates of 4, 7, 10 and 12oC.min-1 were analyzed by the constant rate of heating model and by construction of the master sintering curve. Validation of the master sintering curve was carried out by measurements of density in conventionally sintered specimens. Slight anisotropy of shrinkage data was found and changes to the basic equation of density was proposed to account for this effect. Plotting the data determined by the constant rate of heating model versus density allowed an easy identification of the density range of constant activation energy. The activation energy (865 kJ.mol-1) obtained from the master sintering curve correlates quite well with that (874 kJ.mol-1) obtained by the constant rate of heating model.
关键词： A. Sintering,A. Powders: solid state reaction,E. Fuel cells,D. Perovskites
更新于2025-09-09 09:28:46
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Room temperature multiferroic properties of Fe-doped nonstoichiometric SrTiO3 ceramics at both A and B sites
摘要： This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted nonstoichiometric STO ceramics. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The room temperature multiferroicity of the Fe-doped Ti-rich STO ceramics is successfully realized by M-H hysteresis loop, P-E hysteresis loop and magnetodielectric measurement. The origins of ferroelectricity may be related to the lattice distortions and antisite-like defects with net local dipoles. The ferromagnetism are mainly contributed by the competitions among the double exchange interactions, super-exchange interactions and the non-linear ferromagnetic exchange coupling. In addition, the ordered spin arrangement of the ferromagnetism is formed by the exchange interaction of Fe atom using first principle simulations.
关键词： D. Ferromagnetism,A. Perovskite,E. Solid-state reactions,D. Ferroelectricity
更新于2025-09-09 09:28:46
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[Springer Series in Materials Science] Introduction to Isotopic Materials Science Volume 248 || Energy Band Structure
摘要： Optical probing and manipulation of electron quantum states in isotope-mixed compounds at the nanoscale are key to developing future nanophotonic devices, which are capable of ultrafast and low-power operation. Before beginning a general discussion on the application of isotopic materials science, it is helpful to have the knowledge of the electronic band structure used in materials. The modern view of solid-state physics is based on the presentation of elementary excitations having mass, quasi-impulse, and electrical charge. The base of such view of solid is ideal gas, which described the behavior of the system, e.g., noninteracting electrons. Such an approach to model of elementary excitations as a suitable model for the application of the quantum mechanics for the solution of solid-state physics task. In this chapter, some peculiarities of isotopic materials science will be considered by taking into account the dependence of the properties of elementary excitations on the isotope effect. It is illustrated when the dimensions of a solid are reduced to the size of the characteristic length of electrons in the isotope-mixed materials (de Broglie wavelength, localization length), new physical properties due to quantum effects become apparent. Our intention has been to physics of low-dimensional isotope-based compounds and quantum devices would built up to the treatment of those new electronic, transport and optical properties.
关键词： nanophotonic devices,isotope effect,electronic band structure,solid-state physics,quantum effects,isotope-mixed compounds,quantum mechanics
更新于2025-09-09 09:28:46
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Dielectric, electrical and impedance study of single perovskite Pb(Ni1/3Mn1/3W1/3)O3
摘要： A multiferroic material Pb(Ni1/3Mn1/3W1/3)O3 with ferroelectric and ferromagnetic properties at room temperature is designed for multifunctional applications. A orthorhombic perovskite crystal structure has been assigned for the present perovskite according to the X-ray diffraction patterns. At 1 kHz, dielectric constant (er) increases from 1655 at 298 K to its ?rst maximum 3514 at 457 K referred as magnetic transition. The high values of er in the low frequency range show better dispersion, and with the increase in frequency, a gradual decrease in the er values was observed. The contribution of grain and/or electrode/interface effects in the resistive/capacitive properties was ascertained by the Nyquist plots. An equivalent circuit has been suggested consisting of resistive and capacitive components (R, C, Q) estimates the bulk (grain) and grain boundary resistance and capacitance. The activation energy was found to be greater than 0.2 eV, supporting the conduction mechanism due to hopping of charge carriers.
关键词： Solid-state reaction,Multiferroic material,Dielectric response,Electrochemical impedance spectroscopy,Ceramics
更新于2025-09-09 09:28:46