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Structural and luminescence studies of Sm3+:CaLa4Si3O13 phosphors: An orange-emitting component for WLEDs application
摘要： With the help of the conventional sol-gel process, six different concentrations of CaLa4-xSi3O13:xSm3+ (0.005≤x≤0.09) phosphors were fabricated. For all samples, by XRD crystal structure and luminescence features have been examined. Based on the diffuse reflectance spectrum, for CaLa3.91Si3O13:0.09Sm3+ phosphor, both direct and indirect optical band gaps have been computed. Following measured PLE and PL spectra, we found that samples can be pumped efficiently by n-UV or blue LED chips for obtaining an intense orange emission at 598 nm (4G5/2→6H7/2) upon 403 nm (6H5/2→4F7/2) excitation. CIE color chromaticity coordinates (x, y) for both CaLa4Si3O13:0.005 and 0.09 Sm3+ phosphors are computed following their corresponding emission spectra. Under 365 nm UV lamp, CaLa4Si3O13:0.09 Sm3+ sample exhibits a bright orange color emission. In this work, it was found that the CaLa4Si3O13:0.09 Sm3+ phosphor possesses potentiality for YAG:Ce3+ phosphor color rendering index (CRI) improvement in WLEDs, excited by the blue LED chips.
关键词： CaLa4Si3O13,XRD,Sm3+ ion,CIE,Photoluminescence,Sol-gel
更新于2025-09-23 15:19:57
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Dysprosium activated strontium aluminate phosphor: A potential candidate for WLED applications
摘要： A series of dysprosium activated strontium aluminate phosphors (SrAl2O4:xDy3+: x=0.1, 0.2, 0.3, 0.4 and 0.5 %) are prepared by conventional solid state reaction method. The structure of the prepared phosphors is analyzed by XRD, results confirm that the crystallinity of the synthesized phosphors is monoclinic phase with space group P21. Morphology and microstructure of the synthesized phosphors is analyzed using FESEM and TEM analysis respectively. Optical properties are analyzed by using Raman and PL spectra. The characteristic peak observed at 465 cm-1 corresponds to bending mode of O-Al-O bonds in corners sharing with [AlO4]5- tetrahedral. The strongest PL emission band observed at 470 nm is assigned to 4F9/2 - 6H15/2 transition in blue region under the ultraviolet excitation wavelength of 347 nm. White light is formed by combination of these three colors and is confirmed by CIE chromatic coordinate graph and possible responsible mechanism is explained in detail.
关键词： Raman,SrAl2O4:Dy3+,PL,XRD,TEM,CIE,FESEM
更新于2025-09-23 15:19:57
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Studies on structural, surface morphology and optical properties of Zinc sulphide (ZnS) thin films prepared by chemical bath deposition
摘要： Zinc sulphide (ZnS) thin films have been prepared by chemical bath deposition method. X-ray diffraction (XRD) is used to analyze the structure and crystallite size and scanning electron microscopy is used to study the particle size and morphology of ZnS thin film. Optical studies have been carried out using UV-Visible-NIR absorbance spectrum. The band gap value of the film is calculated and it is found to be 3.45 eV. The dielectric properties of ZnS thin films have been studied in the different frequency at different temperatures.
关键词： scanning electron microscopy (SEM),Zinc sulphide (ZnS) thin films,dielectric studies,X-ray diffraction (XRD)
更新于2025-09-23 15:19:57
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Monitoring the characteristic properties of Ga-doped ZnO by Raman spectroscopy and atomic scale calculations
摘要： We experimentally and theoretically study how the structural and vibrational properties of zinc oxide (ZnO) are modified upon Gallium (Ga) doping. The characteristics of Ga-doped ZnO thin films which are synthesized by sol-gel spin coating method on glass substrates are monitored by using X-ray diffraction (XRD) and Raman scattering measurements. For atomic-level understanding of the experimental findings state-of-the-art density functional theory (DFT) based calculations are also performed. DFT calculations reveal that both the substitution and adsorption of Ga atoms in ZnO are energetically possible and substitutional doping in ZnO is the most favourable scenario. XRD measurements show that all the films are in wurtzite structure and the crystallite size of the films decreases with increasing Ga doping. In addition, Raman analysis show that strong vibrational modes at about 100 and 441 cm?1 are associated with E2low and E2high phonon modes of ZnO, respectively. While the frequency of the E2low downshifts with increasing Ga concentration, the E2high phonon mode is not affected by the Ga doping. Furthermore, EGa phonon branch, stemming from the substituted Ga atoms, emerges at low frequencies. It is also seen that the Raman intensity of the EGa peak linearly increases with increasing Ga concentration. Experimental results on the vibrational properties are in good agreement with the ab initio phonon calculations.
关键词： Thin films,Ga-doped ZnO,XRD,ab initio,Raman spectroscopy
更新于2025-09-23 15:19:57
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Enhancing the structural, optical and electrical properties of ZnO nanopowders through (Al+Mn) doping
摘要： Undoped ZnO and Zn0.97-xAl0.03MnxO (x = 0, 1, 2 and 3%) nanopowders (NPs) were synthesized by co-precipitation method. They were characterized by X-ray diffraction (XRD), Fourier transformed infrared (FTIR), Raman, UV-visible, photoluminescence (PL) and impedance spectroscopies. All samples exhibit a single phase wurtzite type. The average crystallite size lying between 22 and 42 nm was found to increase for all doped ZnO samples. The optical transmission in the visible region was improved due to doping. The optical band gap is in the range of 3-3.4 eV and was found to decrease up to 2% of Mn content but slightly increases with further doping. All PL spectra exhibit two emission peaks in UV and visible regions. The deconvolution of the visible emission peak reveals different emissions for all samples. An additional yellow emission is noticed for (Al+Mn) ZnO doped samples suggesting that the incorporation of aluminum and manganese in the zinc oxide host lattice enhances luminescence properties of ZnO. The ac conductivity (σac) was found to follow Jonscher’s power law and was improved with doping. Cole-Cole plots of all samples were suitably fitted to a circuit consisting in a parallel combination of a resistance and a constant phase element (CPE).
关键词： optical properties,XRD,doping,conductivity,ZnO nanopowder
更新于2025-09-19 17:15:36
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In Situ Raman Spectroscopy on Silicon Nanowire Anodes Integrated in Lithium Ion Batteries
摘要： Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm?1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components.
关键词： silicon nanowires,lithium ion batteries,in situ Raman spectroscopy,operando XRD,solid electrolyte interphase
更新于2025-09-19 17:15:36
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Synthesis and Characterization of Substituted Metal(II)-octa- MethoxyphenylImino Phthalocyanine Pigments
摘要： The synthesis, spectral and magnetic susceptibility on symmetrically substituted metal(II)-octa-methoxyphenyl imino phthalocyanine by condensing octa amino phthalocyanines with o-anisaldehyde are described. The dark green colour octa amino phthalocyanine derivatives were characterized by electronic, IR, elemental analysis, magnetic susceptibility, powder X-ray diffraction and thermo gravimetric analysis (TGA) studies to structural integrity, check the purity and crystalline properties of the pigments. The variation of magnetic moment as function of field strength 2.20 to 4.01 kg indicated the presence of intermolecular co-operative effect
关键词： TGA,Magnetic susceptibility,IR,Electronic,XRD,Octamethoxy imino phathalocynaine
更新于2025-09-19 17:15:36
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Photocatalytic Degradation of Methylene blue with Synthesized rGO/ZnO/Cu
摘要： In order to observe photocatalysts reactions, rGO/ZnO/Cu nano-structure was synthesized through total reflux combined hydrothermal method. The effects of adding rGO and Cu doping on ZnO lattice were assessed. FE-SEM, TEM, EDX analysis, and XRD tests were used to study the morphology and particle size of the catalyst. The XRD-SAXS verified the crystallinity of the catalysts. FTIR and Raman spectroscopy characterized the mineral oxide-GO bonds also DRS was applied to study the band gap. Photocatalytic degradation efficiency was investigated by methylene blue solution and 25 mg photocatalyst is the best dosage for degradation.
关键词： DRS,Photocatalyst,XRD,Zinc oxide,Graphene oxide
更新于2025-09-19 17:15:36
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Evolution of Mechanically Formed Bow Due to Surface Waviness and Residual Stress difference on Sapphire (0001) Substrate
摘要： Single crystalline sapphire is one of the most widely used wafers for modern high-technology electronic and optical devices owing to the well-established mass production, own physical properties with high thermal, mechanical, and chemical stability, and lattice constants suitable for growth of highly crystalline films. When single crystalline wafers are used as substrates, the curvature of the wafer surface usually called bow is inevitable. Since bow can degrade the quality of deposited film by defects generation or undesirable strain at the interface, to reduce the bow and surface roughness, procedures such as lapping, annealing, and polishing are followed after wafer slicing. Although single crystalline sapphire has sufficiently high hardness for the device applications, surface waviness after abrasion and residual stress within wafer can induce bow. In this study, we revealed the mechanism of bow evolution using high-resolution X-ray diffraction and Raman spectroscopy following each wafering steps. We found that bow in single crystalline sapphire wafer is mainly determined by the irregularly abraded surface after wafer slicing at earlier wafering process. This kind of bow is significantly reduced after lapping and annealing procedure. However, additional surface polishing can inflict stress on the surface and increase bow due to residual stress difference between the polishing surface and the opposite surface. While bow can be effectively reduced by further polishing on the opposite surface, the surface lattice remains still strained.
关键词： HR-XRD,Machining process,Residual stress,Sapphire,Bow,Raman spectroscopy
更新于2025-09-19 17:15:36
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Performance of TiO2 Based Dye-Sensitized Solar Cells Fabricated Using Coomassie Brilliant Blue in Acetonitrile Solution
摘要： The synthetic dye sensitizer based solar cells were successfully fabricated and photovoltaic performance was measured. Titanium dioxide (TiO2) nanoparticles were synthesized using sol–gel technique. The XRD and HRTEM analysis were carried out to determine the structural and morphological property of TiO2 nanoparticles. The crystalline sizes of the TiO2 particles were determined by XRD and were confirmed by TEM. The synthetic Coomassie Brilliant Blue (CBB) dissolved in acetonitrile was used as a dye in the nanocrystalline Tio2 solar cell. TiO2 films on FTO glass substrate were prepared by simple doctor blade technique. The dye was characterized by UV-Vis absorption spectroscopic analysis. The strong absorption of the CBB dye enhanced the DSSC property. The results showed that TiO2 as photoanode and CBB as a sensitizers showed good conversion efficiency.
关键词： CBB,DSSC,TEM,XRD,Titanium dioxide
更新于2025-09-19 17:13:59