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Effect of Hf <sup>4+</sup> doping on structure and enhancement of upconversion luminescence in Yb:Tm:LiNbO <sub/>3</sub> crystals
摘要： A series of Yb:Tm:LiNbO3 crystals doped with x mol% Hf4+ ions (x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf4+ ions concentration on UV–VIS–NIR absorption spectra of Hf:Yb:Tm:LiNbO3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf4+ ions.
关键词： crystal structure,Hf:Yb:Tm:LiNbO3 crystals,upconversion luminescence
更新于2025-09-09 09:28:46
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Crystal structure dependence of red to green light emission by LaOF : Yb3+/Er3+ up-conversion phosphor
摘要： Up-conversion (UC) is the conversion of electromagnetic waves from long to short wavelengths. In this study, near-infrared rays (with wavelengths of 980 nm) were upconverted to visible light rays (with wavelengths of 400–750 nm), and the UC luminescence characteristics of lanthanide-doped materials were measured and analyzed. LaOF : Yb3+/Er3+ UC phosphor samples were fabricated by using LaF3 (hexagonal), Yb2O3 (cubic), and Er2O3 (cubic) powders. The mole ratio of La : Yb : Er was 1 : 0.01 : 0.01, and LaOF : Yb3+/Er3+ was obtained by baking these materials. The UC emission of yellow to green light was confirmed by the overlapping of green and red light. The emitted light intensity was the highest for the sample baked at 1100 oC for 2 h. Furthermore, X-ray diffraction (XRD) results revealed that the photoluminescence emission intensity increased with increasing integrated intensity of the tetragonal LaOF crystal system.
关键词： Phosphor,Crystal structure,Up-conversion,Yb3+/Er3+,LaOF
更新于2025-09-09 09:28:46
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A Combined Experimental and Theoretical Investigation on Organic Cation Dichlorocopper (II): Structural Characterization, Hirshfeld Surface Analysis, Spectroscopic Properties and DFT Calculation
摘要： The (ethylenediamine) dichlorocopper(II) complex, {[Cu(en)]Cl2}n(en:C2H8N2), was synthesized by hydrothermal technique. The X-ray structure of {[Cu(en)]Cl2}n shows that the compound crystallizes as a one dimensional chain with one chlorine that is non-bridging and the other chlorine which is triply bridging. It crystallizes at room temperature in the centrosymmetric space group P21/m. The structure of {Cu(en)Cl2}n was originally reported by Kumara et al. The surrounding copper is best described as distorted octahedral. The crystal structure was stabilized with an extensive network of N-H…Cl classical hydrogen bond interactions. The investigation on that close intermolecular interactions between the molecules via Hirshfeld surface analyses is presented to reveal subtle differences and similarities in the crystal structures. The decomposition of the fingerprint plot area provides a percentage of each intermolecular interaction, allowing for a quantified analysis of close contacts within the crystal. The optimized molecular structure and vibrational spectra were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the LanL2DZ basis set. Good consistency is found between the calculated results and the experimental structure, FT-IR, and FT-Raman spectra. The detailed interpretation of the vibrational modes was carried out. Optical transmission measurements performed on thin films of {[Cu(en)]Cl2}n revealed two absorption bands at 3.64 eV and 1.907 eV. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule.
关键词： Optical absorption,Synthesis hydrothermal,Complex copper (II),Hirchfeld surface analysis,Crystal structure,DFT vibrational assignment
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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Synthesis, crystal structure, vibrational study, optical properties and Hirshfeld surface analysis of bis(2,6-diaminopyridinium) tetrachloridocobaltate(II) monohydrate
摘要： The title organic–inorganic hybrid compound, (C5H8N3)2[CoCl4]·H2O, was synthesized by slow evaporation at room temperature. Single-crystal X-ray diffraction analysis indicates that the asymmetric unit in this compound consists of one tetrahedral geometry [CoCl4]2-, two protonated organic cations (C5H8N3)+ and one water molecule of crystallization, all of which lie in general positions. In the crystal structure, the inorganic layers are built from tetrachloridocobaltate anions [CoCl4]2- and free water molecules, linked together by O—H…Cl hydrogen bonds. The organic cations are intercalated between the inorganic layers via N—H…Cl hydrogen bonds and form chains through aromatic donor–acceptor interactions. Crystal cohesion is achieved through N—H…Cl, O—H…Cl, N—H…O and C—H…Cl hydrogen bonds between organic cations, inorganic anions and the water molecules building up a three-dimensional network. The functional groups present in the crystal were studied by FTIR spectroscopy. Investigation of the optical properties of the compound confirmed its semiconducting properties by revealing a direct optical band gap at 1.67 eV. Photoluminescence proprieties were also reported. The three-dimensional Hirshfeld surface (3D-HS) analysis and the two-dimensional fingerprint plots (2D-FP) reveal that the structure is dominated by H…Cl/Cl…H and H…H contacts.
关键词： Crystal structure,Hirshfeld surface analysis,Vibrational study,Cobalt complex
更新于2025-09-09 09:28:46
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Gallium Oxide || Ga2O3-based gas sensors
摘要： β-Ga2O3 has recently gained a lot of interest for applications in solar-blind deep ultraviolet (UV) detectors and high-power electronics at elevated temperatures. The interest stems from its intrinsic material properties, such as wide-bandgap nature (4.9 eV) and high breakdown electric field. β-Ga2O3 can also serve as a reactive oxide layer, sensitive to a wide variety of gases, especially at high temperatures in harsh environments. Many β-Ga2O3-based gas sensors have been reported recently [1–20]. In this chapter, the gas sensing mechanism and the sensing characteristics of β-Ga2O3 are reviewed. First, the material properties of β-Ga2O3 are reviewed for a clear understanding of surface reactions at oxide surfaces with various gas molecules. The crystal structure of β-Ga2O3 and the surface atomic configurations of 201 and (010)-oriented β-Ga2O3 are investigated. The wet and dry etching characteristics and the metal contact properties of 201 and (010) β-Ga2O3 single crystals are discussed for a broad range of device applications. Recent reports of β-Ga2O3-based hydrogen sensors are discussed, and the hydrogen sensing properties of 201 and (010) β-Ga2O3 single crystals are compared for enhanced hydrogen detection.
关键词： crystal structure,β-Ga2O3,high-temperature applications,wet and dry etching,Ohmic contact,gas sensors,hydrogen sensors
更新于2025-09-09 09:28:46
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Synthesis, photoluminescence and thermodynamics of two lanthanide coordination polymers with 5-nitroisophthalate
摘要： Two lanthanide-based metal–organic frameworks, [Tb2(5-nip)3(H2O)5·5H2O]n (1), and [Eu3(5-nip)4(5-Hnip)(H2O)7·9H2O]n (2) (5-H2nip = 5-nitroisophthalic acid), have been synthesized and structurally characterized. 1 features a unique 3D network with two distinct paddlewheel building blocks. 2 displays a 3D supramolecular framework with 1D channels occupied by free water molecules. Solid-state photoluminescence studies indicate that both the compounds 1 and 2 exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region at room temperature. TG-DSC curves show that the dehydrated products of the title compounds exhibit high stability up to 400 °C. The enthalpy changes of liquid-phase reaction of formation for 1 and 2, (l), were determined at 298.15 K by a microcalorimeter to be (10.7 ± 0.1) kJ·mol-1 and (30.6 ± 0.1) kJ·mol-1, respectively. Based on a designed thermochemical cycle, that of solid-phase reaction of formation and the standard molar enthalpy of formation for 1, (s) and , were calculated to be (16.9 ± 0.6) kJ·mol-1 and -(3103.2 ± 15.3) kJ·mol-1, respectively. Those for 2 were (119.4 ± 0.8) kJ?mol-1 and -(4510.2 ± 17.4) kJ?mol-1, respectively. Combining the thermochemical data of the reactions and kinetic equations with the data of thermokinetic experiments, the fundamental thermodynamic and kinetic parameters were also achieved.
关键词： Microcalorimetry,Thermochemistry,Photoluminescence,Crystal structure,Lanthanide
更新于2025-09-09 09:28:46
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Protoenstatite in MgSiO<sub>3</sub> samples prepared by conventional solid state reaction
摘要： Enstatite (MgSiO3) sample was prepared by conventional solid state reaction at 1500 °C, followed by cooling to ambient temperature with different cooling rates (0.04–500 °C/s). Quantitative analysis of enstatite phases in the samples by Rietveld re?nement and 29Si MAS NMR revealed that a large amount of metastable protoenstatite (30–40 mol%) along with clinoenstatite was preserved in all samples. The presence of protoenstatite was also con?rmed by micro–Raman spectroscopy. The crystal structures of protoenstatite and clinoenstatite at room temperature were re?ned using the Rietveld method, and were essentially the same as those reported by previous studies. As the solid state reaction method is commonly used to prepare synthetic clinoenstatite, the present result implies that the ‘clinoenstatite’ starting materials used in previous phase equilibrium studies of MgSiO3 pyroxene might contain overlooked protoenstatite, which could affect the interpretation for phase transition and thus those results should be reexamined.
关键词： MgSiO3,Clinoenstatite,Protoenstatite,Crystal structure,Phase relation
更新于2025-09-09 09:28:46
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Heteroleptic complexes of silver(I) featuring 4′-hydroxy- and 4′-(2-furyl)-2, 2′:6′, 2″-terpyridine: an easy route to synthesis silver nanoparticles
摘要： New coordination complexes of silver(I) containing triphenylphosphine and 4′-hydroxy-2,2′:6′,2″-terpyridine (tpyOH) or 4?-(2-furyl)-2,2′:6′,2″-terpyridine (ftpy) have been synthesized to afford the new compounds [Ag(tpyOH)(PPh3)](NO3) (1) and [Ag(ftpy)(PPh3)](NO3) (2). In addition, the reaction of silver(I) nitrate with ftpy in the presence of excess of 4,4′-bipyridine (bpy) and NH4PF6 led to the formation of binuclear complex [Ag2(ftpy)2(μ-bpy)](PF6)2 (3). The products have been characterized by elemental analysis, IR, UV-Vis, NMR (1H, 31P) spectroscopy and single crystal X-ray diffraction in the case of 3. The 31P NMR data reveal that the interaction of PPh3 with silver(I) is maintained in solution in 1-2. The crystal structure of 3 shows that each Ag+ ion is coordinated by three N-atoms of ftpy and a nitrogen from the bridging ligand of bpy in a slightly distorted square planar geometry. There are some strong noncovalent interactions of hydrogen bonding and Ag-η2-furyl in the crystal structure, connecting molecules to form a supramolecular network. The thermal decomposition of 1-3 has also been investigated. The thermal stability of all complexes, as determined by thermogravimetric analysis (TGA), are almost the same and they are thermally stable up to 220 oC. The complex 3 was used for the preparation of Ag nanoparticles by simple calcination method at two different temperatures of 400 and 600 ?C resulting in the formation of silver nanoparticles, crystalline in nature with the size of 66 and 52 nm, respectively, using Scherrer’s equation. The nano-sized silver particles have also been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDX).
关键词： Crystal Structure,Thermal Properties,Nano Particle,Silver,Terpyridine
更新于2025-09-09 09:28:46
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Structural and optical properties of (Cu6PS5Br)1-(Cu7PS6) mixed crystals
摘要： The structure and optical properties of Bridgman-grown (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals are reported. X-ray diffraction data reveal a face-centred cubic lattice (Fm-34 space group) for Cu6PS5Br-rich crystals (0<x<0.4) and a primitive cubic lattice (P213 space group) for Cu7PS6-rich (0.4<x<1) crystals. These structural data correlate with the Raman spectra where, besides the common features typical for the argyrodite-type Cu6PS5Br and Cu7PS6 crystals, weaker bands characteristic only for the end-point compounds are observed in the corresponding compositional intervals. Based on the spectral position of the short-wavelength edge of diffuse reflection spectra, the compositional dependence of the energy gap is studied exhibiting a nonlinear behaviour.
关键词： Inorganic materials,crystal growth,diffuse reflection,Raman scattering,X-ray diffraction,crystal structure
更新于2025-09-04 15:30:14