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Eu3+ doped (Li, Na, K) LaMgWO6 red emission phosphors: An example to rational design with theoretical and experimental investigation
摘要： Various theoretical methods were comprehensively applied in (Li, Na, K) LaMgWO6: Eu3+ phosphors to achieve the rational design of phosphors. The detailed structural characteristics were analyzed by using geometric optimization and Rietveld analysis for the first time. The plane-wave density functional theory (DFT) was used for all electronic structure, electronic distribution, and phonon dispersion calculations. The evolution of the octahedral tilting in the (Li, Na, K) LaMgWO6 crystal structures was studied in detail. The relationship between crystal structure, environmental factors, Judd-Ofelt intensity parameters and fluorescence properties were analyzed. Combined with experimental results and theoretical calculations, the detailed luminescence process is deduced starting from the different ionic radius of Li+, Na+, and K+. Notably, the redshift of CTB can be ascribed to the value variation of environmental factors, which can represent the ionic radius, coordination number, covalency, and polyhedral tilting to qualify comparison and even quantify analysis.
关键词： Red emission,Phosphor,Double perovskite tungstate,Luminescence,CASTEP,Environmental factor
更新于2025-09-19 17:15:36
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Synthesis, structure and optical properties of Erbium-doped Lithium Barium Phosphate
摘要： Li2BaP2O7 activated with Er3+ ions was prepared by the classic ceramic method and characterized by X-ray diffraction technique, IR, Raman and photoluminescence (PL) spectroscopies. The Li2BaP2O7: Er phosphors exhibited a monoclinic single phase structure with C2/c space group. A green and red emission lines dominate the spectrum upon excitation at 400 nm. The CIE-coordinate (x = 0.308, y = 0.512) were found in green light. Free ion parameters of the Er3+ ions in Li2BaP2O7 and the Judd–Ofelt parameters were calculated and they were used to explore the radiative parameters such as transition probability (AT), and branching ratios (β) related to the Er3+ emission transitions. The calculated 4S3/2 radiative life time around 0.198 ms is compared with the experimental value. The calculated quantum efficiency is about 42 %. Li2BaP2O7: Er can be considered as a novel green phosphor.
关键词： Erbium,green phosphor,Judd-Ofelt theory,optical spectroscopy
更新于2025-09-19 17:15:36
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Mn <sup>4+</sup> -activated BaLaMgSbO <sub/>6</sub> double-perovskite phosphor: a novel high-efficiency far-red-emitting luminescent material for indoor plant growth lighting
摘要： In the present work, novel high-efficiency Mn4+-activated BaLaMgSbO6 (BLMS) far-red-emitting phosphors used for plant growth LEDs were successfully synthesized via a solid-state reaction method. X-ray diffraction (XRD), photoluminescence (PL), temperature-dependent PL, CIE color coordinates, and lifetimes as well as internal quantum efficiency (IQE) were used to characterize the phosphor samples. The excitation spectrum of the as-obtained BLMS:Mn4+ phosphors presented two wide bands covering 250–550 nm and the emission spectrum exhibited a far-red emission band in the range of 650–800 nm peaked at 700 nm. Concentration-dependent PL properties of BLMS:Mn4+ phosphors were studied. The optimal doping concentration of Mn4+ ions was 0.6 mol%, and the concentration quenching mechanism was determined to be the nonradiative energy transfer among the nearest-neighbor Mn4+ activators. Impressively, the BLMS:0.6%Mn4+ sample showed an outstanding IQE of 83%. In addition, the luminescence thermal quenching characteristics were also analyzed. Furthermore, the PL spectrum of BLMS:0.6%Mn4+ sample was compared with the absorption spectrum of phytochrome PFR. Finally, after combining BLMS:0.6%Mn4+ phosphors with a 365 nm near-UV LED chip, a far-red light-emitting diode (LED) device was successfully achieved to demonstrate its possible applications in plant growth LEDs.
关键词： far-red-emitting,solid-state reaction,Mn4+-activated,internal quantum efficiency,plant growth LEDs,phosphor,BaLaMgSbO6
更新于2025-09-19 17:15:36
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Studies on pelletized lithium magnesium borate TL material for eye lens dosimetry
摘要： Recent epidemiological studies in various cohorts confirm that radiation induced cataract may occur at a threshold dose as low as 0.5 Gy. ICRP has recognized the higher radiosensitivity of eye lens and recommended to reduce annual eye lens dose limit from 150 mSv to 20 mSv. Present dosimetry for eye lens is largely based on LiF based dosimeters. The present work is an attempt towards using near tissue equivalent lithium borate material namely lithium magnesium borate doped with terbium (LMB:Tb) in eye lens dosimetry. The material in powder form was synthesized using solid state sintering method and pelletized using poly tetra fluoro ethylene (PTFE) as binding agent. It was observed that 130 mg of 1mm thick LMB:Tb pellet bound with PTFE showed stable glow curve structure and attractive dosimetric features in terms of sensitivity, fading, linearity, reusability etc. A proposal of 1.5 mm Teflon encapsulation corresponding to tissue equivalent thickness of 3 mm was put forward for an ideal dosimeter for the measurement in terms of Hp(3). Energy and angular dependence studies based on FLUKA simulations suggest a flat response for the prototype design. In addition to PTFE, various tissue equivalent encapsulations such as polyimide, polyamide 6 and PMMA were also evaluated using FLUKA code.
关键词： thermoluminescence,Eye lens dosimetry,lithium borate phosphor
更新于2025-09-19 17:15:36
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Structural, photoluminescence and dielectric investigations of phosphatic shale
摘要： In the current study, the structural and spectroscopic properties of phosphatic shale samples obtained from the Atomic Minerals Directorate for Exploration and Research were probed for potential use as a phosphor material. X‐ray diffraction and Raman and Fourier transform infrared spectroscopy revealed that the beneficiated phosphatic shale samples were primarily monophasic consisting of fluorapatite [Ca5(PO4)3F, (FAP)] with minor traces of haematite (α‐Fe2O3) and calcite (CaCO3). Energy dispersive X‐ray fluorescence revealed the presence of U, Eu, Dy and Tb in the FAP matrix substituted at Ca(I) and Ca(II) sites of FAP. A reduced optical direct band gap of 4.46 eV was calculated from the Tauc plot. Photoluminescence spectral studies revealed multicolour emissions (red, yellow, green and blue) on ultraviolet light excitation that were attributed to luminescence spectra from rare earth ions Eu3+, Tb3+, U4+ and U6+ in the FAP matrix. The overall emissions for the rare earth and actinide‐doped FAP were obtained in the cool white region and the corresponding Commission Internationale de l’Eclairage chromaticity coordinates were calculated to be (0.274, 0.317). The corresponding colour correlated temperature obtained was 9342 K. Furthermore, phosphatic shale had a high room temperature dielectric constant of 11 at a frequency of 1 kHz that demonstrated its suitability for use in biological sensors. The study showed that natural phosphatic shale could be a potential material for optical, biological and dielectric applications.
关键词： dielectric studies,photoluminescence,phosphor,X‐ray diffraction
更新于2025-09-19 17:15:36
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Optical spectroscopy of thermal stable Na2ZnP2O7: Sm3+/ (Li+, K+) phosphors
摘要： Na2ZnP2O7 pyrophosphates doped with different concentrations of Sm3+ were synthesized successfully via a solid-state reaction process. A vibrational Raman-IR spectroscopic and diffraction analysis has been performed. The Na2ZnP2O7: Sm3+ powders were crystallized in a tetragonal lattice with P42/mnm space group. The photoluminescence (PL) emission and PL excitation (PLE) spectra were studied as a function of Sm3+ concentration. The optimal Sm3+ doping concentration in Na2ZnP2O7 host matrix is determined to be 1 mol%. In order to enhance the luminescent intensity of these phosphors, the compensator charge Li+ and K+ ions were introduced in the Na2ZnP2O7 host. Furthermore, the luminescence of Na2ZnP2O7: Sm3+ indicates good thermal stability at high temperatures. The chromaticity diagram of the Commission International de l'Eclairage (CIE) was investigated, indicating a bright orange-red emission. Hence, the obtained results indicate that the as-prepared phosphor can be a potential candidate for application in Light Emitting Diodes (LEDs).
关键词： thermal stability.,Orange-red phosphor,Na2ZnP2O7,Luminescent material
更新于2025-09-19 17:15:36
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Structural micro-modulation on Bi3+ doped Ba2Ga2GeO7 phosphor with considerable tunability of the defect-oriented optical properties
摘要： We report a new Ba2Ga2GeO7:Bi3+ phosphor with broad emission almost covers the entire visible area generated from different bismuth emission centers in crystalline structure. The two peaks positions are invariably located at 497 and 611 nm which were independently excited by 365 and 387 nm excitation sources. As the emission tightly relies on the excitation source in an extremely wide range (260 to 470 nm), the emission color can be easily manipulated from cyan to red. The WLEDs devices with Ra = 90.40 and 91.98 were fabricated by employing Ba2Ga2GeO7:0.012Bi3+ as a red component phosphor. Through analyzing, we found P2 (Ga/Ge) sites tend to form vacancies in the sintering process. When bismuth concentration is set fixed, the luminescent intensity is quite dependent on the quantity of Ga or Ge vacancies which are beneficial to form Bi3+ emission centers and provide a fresh idea for structural micro-modulation. Our results also provide new insights for understanding the roles of the vacancy played in phosphors.
关键词： luminescence,bismuth,color-tunable,WLEDs,phosphor,vacancy
更新于2025-09-19 17:15:36
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Effect of Bi <sup>3+</sup> ion on upconversion-based induced optical heating and temperature sensing characteristics in the Er <sup>3+</sup> /Yb <sup>3+</sup> co-doped La <sub/>2</sub> O <sub/>3</sub> nano-phosphor
摘要： The upconversion-based optical heating and temperature sensing characteristics are investigated in the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor synthesized through a solution combustion method. The structural measurements reveal an increase in lattice parameters and particles size of the phosphor on increasing the concentrations of Bi3+ ions. The energy dispersive spectroscopic (EDS) measurements confirm the presence of La, Er, Yb, Bi and O elements in the tri-doped phosphor. The absorption spectra show the large number of bands due to Er3+, Yb3+ and Bi3+ ions. The Er3+/Yb3+ co-doped phosphor gives strong green emission bands at 523 and 548 nm upon 976 nm excitation due to 2H11/2 / 4I15/2 and 4S3/2 / 4I15/2 transitions of Er3+ ion, respectively. The emission intensity of these bands is enhanced upto 15 times in the presence of Bi3+ ions. The emission intensities of the 523 and 548 nm bands vary non-linearly with the pump power. The fluorescence intensity ratio (FIR) of the thermally coupled 523 and 548 nm emission bands shows efficient optical heating in the tri-doped phosphor. The FIR of the 523 and 548 nm emission bands further varies with the increase in temperature of the phosphor. The relative temperature sensing sensitivity has been calculated to be 71 × 10?4 K?1 at 450 K for the tri-doped phosphor. Thus, the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor may provide a platform to use it in the photonic devices, as an optical heater and temperature sensor.
关键词： La2O3 nano-phosphor,temperature sensing,optical heating,solution combustion method,Er3+/Yb3+/Bi3+ tri-doped,upconversion
更新于2025-09-19 17:15:36
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The Study on Titanium Dioxide-Silica Binary Mixture Coated SrAl2O4: Eu2+, Dy3+ Phosphor as a Photoluminescence Pigment in a Waterborne Paint
摘要： After proper stimulation, long afterglow phosphors formulated as pigment in waterborne paints can emit light after the removal of the excitation light source. The encapsulation of SrAl2O4: Eu2+, Dy3+ phosphor by TiO2 and SiO2 individually, and in combination by a precipitation method was studied. The water resistance and photoluminescence behavior of the coated phosphors as a pigment for potential use in waterborne photoluminescence paints were evaluated. It revealed that the TiO2- SiO2 content coating layer was precipitated on the studied phosphor successfully. The higher trend of the TiO2 for coating on the phosphor when compared with the SiO2 was observed from EDS spectra. The SEM micrographs showed a continuous and uniform SiO2-TiO2 layer on the coated phosphor. Based on XRD results, the existence of the TiO2 in the coating layer had beneficial effect on the average crystallite size values. The pH solution versus time showed that the availability of the TiO2 in coated layer improved water resistance of the coated phosphor, although, in comparison with SiO2, it was less effective. The coated phosphor with TiO2 had the minimum afterglow brightness decay and consequently, it was recommended as a suitable pigment for waterborne photoluminescence paints.
关键词： TiO2,SiO2,Pigment,Phosphor,Coating,Waterborne paint
更新于2025-09-19 17:15:36
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Luminescent colour modulation of a multicolour praseodymium activated phosphor
摘要： A phosphor is a material that emits luminescence under stimuli. A 4f-4f RE3+ ion commonly shows an invariable luminescent colour due to the shielding of outer electrons. Here, a multicolour Pr3+-activated phosphor is developed. The luminescent colour of Pr3+ in the phosphor can be modulated from red to white. This investigation reveals that this modulation essentially corresponds to the different relaxation pathways of Pr3+ levels in low-phonon-energy hosts. Based on the specific characteristics of the phosphor, a multicolour image is fabricated for application in anticounterfeiting.
关键词： Rare earth,Luminescent colour,Phosphor,Luminescence
更新于2025-09-19 17:15:36