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Comparative study of Sm3+ ions doped phosphate based oxide and oxy-fluoride glasses for solid state lighting applications
摘要： The physical and luminescent properties of Sm3+-doped oxide and oxy-fluoride phosphate glasses were investigated. The glass samples with chemical composition of 69P2O5-10BaO-10ZnO-10Gd2O3-1Sm2O3 and 69P2O5-10BaO-10ZnO-10GdF3-1Sm2O3 were prepared by conventional melt quenching technique. The prepared glass samples were characterized with density, molar volume, refractive index, FTIR, UV-Vis-NIR, photoluminescence, radio luminescence, decay time profile, and CIE diagram. The density and refractive index of the oxide glass have higher values as compared to the oxy-fluoride glass. The FTIR spectra show the reduction of O-H group in oxy-fluoride glass. The characteristic peaks of Sm3+ are observed at 360, 372, 402, 438, 419, 473, 944, 1077, 1227, 1373, 1474, 1529 and1585 nm in UV-VIS-NIR spectra. These peaks are related respectively to the transitions from ground state 6H5/2 to 4D3/2, 6P7/2, 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 excited states. From photoluminescence and radio-luminescence it is observed that the oxy-fluoride glass samples show better emission intensity than the oxide glass. The Judd-Ofelt theory (J-O theory) was used to find J-O intensity ?λ (λ=2,4 and 6) parameters and radiative properties such as transition probability, stimulated emission cross section and branching ratios for titled glasses. The trend observed in the J-O parameters is ?4 >?2 >?6. The transition probability, emission cross section and branching ratio have the highest values for the 4G5/2→6H7/2 transition. The CIE coordinates of the prepared glass samples are positioned in the orange region and the CCT value is 3776.105 for oxide and oxyfluoride glass. The oxy-fluoride glass has shorter decay time as compared to the oxide glass and it is recorded to be 1.62 and 1.32 ms for oxide and oxy-fluoride respectively. According to the results obtained in this work, it is obvious that these glass samples can be good candidate materials for producing cool orange light.
关键词： Judd-Ofelt theory,Oxy-fluoride glass,Rare earths,Photoluminescence,CIE coordinates
更新于2025-09-23 15:23:52
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Synthesis, Structural and Luminescent Properties of Eu2+/Dy3+ Activated GdAlO3 Phosphors by Solid State Reaction Method Under Nitrogen Atmosphere
摘要： Synthesis, Structural and Luminescent Properties of Eu2+/Dy3+ Activated GdAlO3 Phosphors by Solid State Reaction Method Under Nitrogen Atmosphere. Eu2+ and Dy3+ singly doped and codoped GdAlO3 phosphor was synthesized by solid state reaction method in a reducing atmosphere of nitrogen. Samples were characterized by powder X-ray diffraction (PXRD) analysis. The average crystal size was obtained around 48 nm. Surface morphology was verified by scanning electron microscopy (SEM) analysis. The emission spectra of phosphors singly doped with Eu2+ and codoped with Eu2+; Dy3+ respectively were recorded under 354 nm excitation. The emission spectra of Eu2+ has intense emission peak at 515 nm. It was observed that the after codoping with Eu2+ and Dy3+ the emission bands of Eu2+ dominates along with a new emission band centred at 419 nm. CIE chromaticity diagram shows variation in emitted colour with Eu2+, Dy3+ singly doped and codoped phosphor. The investigation of Dy3+ codoping shows the colour tunable behaviour of the phosphor. This colour tunable behaviour of the phosphor makes it useful in the colour display applications.
关键词： CIE,XRD,Eu2+,photoluminescence,GdAlO3,Dy3+
更新于2025-09-23 15:22:29
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Enhancement of luminescence intensity and spectroscopic analysis of Eu3+ activated and Li+ charge-compensated Bi2O3 nanophosphors for solid-state lighting
摘要： The present work reports the synthesis, characterization, photoluminescence and photocatalytic activity of Eu3+ (1-11 mol %) doped and Li+ (0.5-5 mol %) co-doped Bi2O3 nanophosphors (NPs) by sonochemical method. The average particle size was estimated using powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) and found to be in the range of 30 to 35 nm. The scanning electron microscopy (SEM) images were highly dependent on sonication time and concentration of Epigallocatechin gallate (EGCG) bio-surfactant. The energy gap of doped and co-doped Bi2O3 nanophosphors was estimated using Kubelka-Munk (K-M) function and found to be in the range 2.9-3.08 eV. The effect of Li+ co-doping on luminescence of optimized Bi2O3:Eu3+ was studied and found about more than 3 fold enhancement of emission intensity. Judd–Ofelt parameters (Ω2, Ω4 and Ω6), transition probabilities (AT), quantum efficiency (η), luminescence lifetime (τrad), color chromaticity coordinates (CIE) and correlated color temperature (CCT) values were estimated from the emission spectra and discussed in detail. The estimated CIE chromaticity co-ordinates were very close to the NTSC (National Television Standard Committee) standard value of red emission. The synthesized NPs show excellent photocatalytic activity of Acid red-88 under UV-light irradiation, which can degrade 98.1 % in 60 min. The decreasing electron-hole pair recombination rate with quick electron transfer ability was predominantly ascribed to the balance between crystallite size, morphology, band gap, defects, surface area etc. These results through a light for the use of sonochemical route of Bi2O3:Eu3+:Li+ in solid state display and photocatalytic applications.
关键词： Photoluminescence,Sonochemical,Bi2O3:Eu3+:Li+,Photocatalysis,CIE n CCT
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Analytical Estimation of Optical Efficiency of Cylindrical Light-Tubes Under Various CIE Sky Types
摘要： The light pipes represent a common device for enhancement of daylight amount in buildings with complex architecture and insufficient lighting by vertical windows or in underground spaces. The advantage of straight vertical light pipes is that they transport light into interior spaces from the whole sky vault independently on solar azimuth. So mainly at higher solar altitudes and under clear sky conditions they can significantly contribute in buildings. The optical efficiency of a light pipe strongly depends on number of reflections of the light beams between the particular interfaces. There are available some numerical tools based on ray-tracing algorithms that enable to calculate the efficiency with high precision under given conditions. However, such calculations are adequately time-consuming and so non- attractive for routine (mass) modelling. This contribution presents an analytical method for prediction of the optical efficiency of straight light-pipes which is applicable on 15 types of sky luminance defined by CIE. Due to the analytical approach, the calculation is very fast. The method is validated by accurate numerical simulations for all the sky types and at various pipe aspect ratios. Mainly in the extreme cases of clear and overcast sky, the results are in good agreement.
关键词： light pipe,analytical prediction,optical efficiency,CIE sky models
更新于2025-09-23 15:21:21
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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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Spectroscopic and luminescence properties of Ho3+ ions doped Barium Lead Alumino Fluoro Borate glasses for green laser applications
摘要： Optically transparent Barium Lead Alumino Fluoro Borate (BaPbAlFB) glasses doped with different concentrations of Ho3+ ions were prepared by using melt quench technique. Raman spectral studies were conducted to understand the structural groups present in the as prepared glasses at room temperature. Spectroscopic investigations such as optical absorption, excitation, emission and decay measurements were conducted to understand the visible photoluminescence (PL) and lasing potentialities of BaPbAlFB glasses. The bonding parameters (δ) estimated from the absorption spectral features were used to understand the nature of bonding between Ho3+ ions and the surrounding ligands. The Urbach energy values estimated from the absorption spectral data are used to verify the amorphous nature of the present glass system. The Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to estimate the best fit J-O parameters (?λ, λ= 2, 4, and 6) useful in evaluating various radiative parameters for the prominent fluorescent levels of Ho3+ ions in BaPbAlFB glasses. The experimental lifetimes (τexp) are found to be decreasing with increase in Ho3+ ion concentration owing to energy transfer. The quantum efficiency (η) of Ho3+ ions doped BaPbAlFB glasses were estimated by correlating the experimental lifetimes (τexp) with the radiative lifetimes (τR). The strong visible emission, large stimulated emission cross-section (σse), high branching ratio (βR) and relatively good quantum efficiency (η) obtained for 5S2→ 5I8 (green) transition of 1mol% of Ho3+ ions doped BaPbAlFB glass reveals its suitability in designing and developing visible green lasers.
关键词： emission cross-sections,Holmium,glasses,quantum efficiency,CIE coordinates,photoluminescence
更新于2025-09-19 17:13:59
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Temperature-Dependent Luminescence of Red-Emitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for Near-UV LEDs
摘要： Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing e?ciency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very e?cient red-emitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.
关键词： Eu3+,ceramics,near-UV LED,quantum e?ciency,luminous e?cacy,red phosphor,borate,CIE 1931 colour coordinates,thermal quenching
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Advances in Big Data, Computing and Data Communication Systems (icABCD) - Winterton, South Africa (2019.8.5-2019.8.6)] 2019 International Conference on Advances in Big Data, Computing and Data Communication Systems (icABCD) - A Sensor for Monitoring the Lifespan of Color-LEDs in Traffic Lights
摘要： This paper has explored an effective monitoring of Red, Green and Yellow colors using visible-light communication systems (VLC) as a backbone on traffic lights for easy detection of traffic control light colors in South Africa as well as African continent in context to the problem of consistency in the ON state of traffic control frequency information of detected colors is employed to determine their state for prompt response to the road users. The lifespan of each light emitting diode (LED) dies gradually due to constant heat in the ON-state thus leave some traffic lights not attended. This negligence is because of weak network monitoring techniques which result in vehicle-to-vehicle accidents (V2V), vehicle-to-pedestrian accidents (V2P) and vehicle-to-motorcycle (V2M) accidents. The researchers deploy a TCS3200 pixel color sensor to monitor the lifespan of each LED color in the traffic light and using their variation in frequency to yield the LEDs lifespan, linking them with one central network for display. This experiment guarantees the road users of a steady traffic light to regulate the passing of vehicles without any accident both in frost, high winds and raining season.
关键词： RGB LEDs,Visible light communication (VLC),intensity,CIE 1931
更新于2025-09-16 10:30:52
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Spectral Image Processing for Museum Lighting Using CIE LED Illuminants
摘要： This work presents a spectral color-imaging procedure for the detailed colorimetric study of real artworks under arbitrary illuminants. The results demonstrate this approach to be a powerful tool for art and heritage professionals when deciding which illumination to use in museums, or which conservation or restoration techniques best maintain the color appearance of the original piece under any illuminant. Spectral imaging technology overcomes the limitations of common area-based point-measurement devices such as spectrophotometers, allowing a local study either pixelwise or by selected areas. To our knowledge, this is the ?rst study available that uses the proposed CIE (Commission Internationale de l’éclairage) light-emitting diode (LED) illuminants in the context of art and heritage science, comparing them with the three main CIE illuminants A, D50, and D65. For this, the corresponding colors under D65 have been calculated using a chromatic adaptation transform analogous to the one in CIECAM02. For the sample studied, the CIE LED illuminants with the lowest average CIEDE2000 color di?erences from the standard CIE illuminants are LED-V1 for A and LED-V2 for D50 and D65, with 1.23, 1.07, and 1.57 units, respectively. The work studied is a Moorish epigraphic frieze of plasterwork with a tiled skirting from the Nasrid period (12th–15th centuries) exhibited in the Museum of the Alhambra (Granada, Spain).
关键词： CIEDE2000,hyperspectral line scanner,CIE illuminants,colorimetry,spectral imaging
更新于2025-09-12 10:27:22