Application Of Lamps Research Articles

Luminescence Characteristics of Eu and Tb Doped YGdBO3 Phosphor

Abstract The main aim of this paper is to synthesize rare earth doped phosphors for display applications in Compact fluorescent Lamps (CFLs) and test the utility of these phosphors in accidental radiation dosimetry. The present paper reports the Photoluminescence (PL) and Thermoluminescence (TL) characteristics YGdBO3 doped with Eu and Tb phosphors. The method of preparation followed is a standard solid state reaction (SSR). The PL observed with excitation at 254 nm for the YGdBO3 doped with Eu generates emission at 367, 454,595, 611 and 628 nm. The intensity of peak at 366 nm is relatively less as compared to 594, 613 and 629nm peaks. Photoluminescence spectra of YGdBO3: Tb3+(0.5%) being excited with 254 nm generates an emission at 367, 470,489, 497 and 545 nm. The PL emission at 545 nm is very sharp and followed by a hump at 554 nm. The peak observed at 367 in both the specimens are normally due to crystal field. Thermoluminescence studies of beta irradiated YGdBO3: Eu and Tb3 did show good well defined high intensity isolated TL peak around 200oC. The calculated trap depth is 0.4ev. The TL dosimetry (TLD) studies are interesting. It is proposed the YGdBO3: Tb3+ can be used as lamp as well TLD phosphor in the case of accidental radiation monitoring. It is found the YGdBO3:Tb3+ phosphors can act as phosphor in compact fluorescent lamps as well as a radiation detector in case of accidental nuclear fallout like recent one in Japan, a two in one concept.

Temperature-dependence of the structural and afterglow luminance properties of polymer/SrAlxOy:Eu2+,Dy3+ composites

Although aluminate phosphors have attracted great interest for applications in lamps, cathode ray tubes and plasma display panels, there still remain issues affecting operational parameters such as luminescence efficiency, stability against temperature, high color purity and perfect decay time. In addition, issues involving important aspects of the monoclinic↔hexagonal phase transition temperature still exist. In this work, SrAlxOy:Eu2+,Dy3+ phosphor powders were prepared by the sol–gel method. X-ray diffraction (XRD) has shown that both crystallinity and crystallite sizes increased as the temperature increased. Both SrAl2O4 and Sr2Al3O6 phases were observed. Photoluminescence (PL) characterization shows temperature-dependence, which indicates emission at low and high annealing temperatures originating from Eu2+ and Eu3+ ions. Thermoluminescence glow and decay measurements provided useful insight on the influence of traps on luminescence behavior. Differential scanning calorimetry (DSC) and thermogravimetric studies (TGA) on composites of the phosphor in low density polyethylene (LDPE) demonstrated the varied influence of annealing temperature on some luminescence and thermal properties.

Combustion Synthesis and Luminescence Properties of NaY1-XTbX(WO4)2 Novel Green Phosphors

NaY1-xTbx(WO4)2 green phosphors have been synthesized by a facile combustion method. The structure, morphology and luminescence properties of as-synthesized phosphors were characterized via X-ray powder diffraction (XRD), photoluminescence spectra, and decay curve. The XRD results indicate that as-synthesized phosphors exhibit sheelite-type structure without any impurity phase. The as-obtained phosphors emit strong green light centered at 546 nm under ultraviolet light excitation. The lifetimes are about 0.57 ms. The excellent luminescence properties make it a new promising green phosphor for fluorescent lamps application.

A Study on the Luminescence and Energy Transfer of Green-Emitting Ca9Y(PO4)7:Ce3+,Tb3+ Phosphor for Fluorescent Lamp Application

A Study on the Luminescence and Energy Transfer of Green-Emitting Ca9Y(PO4)7:Ce3+,Tb3+ Phosphor for Fluorescent Lamp Application

Application of Wood's lamp in the diagnosis of superficial cutaneous fungal infections.

Objective To estimate the performance of Wood's lamp examination in the diagnosis of superficial cutaneous fungal infections. Methods Totally, 129 patients, who were diagnosed with superficial cutaneous fungal infections according to clinical medical history and signs, were enrolled in this study. Wood's lamp examination of lesions was carried out. Cutaneous samples were obtained from the patients and subjected to microscopic examination and fungal culture. Results Wood's lamp examination was positive in 84% and 85.7% of patients with tinea versicolor and malassezia folliculitis, respectively; among these patients positive for Wood's lamp examination, 92.9% were positive for fungal culture, and 87.5% for microscopic examination. In patients clinically diagnosed with tinea manus and pedis, tinea corporis or tinea cruris, 8.3% were positive for Wood's lamp examination, while 85.4% were positive for fungal examination. There was a high consistency between Wood's lamp examination and fungal examination in patients with tinea versicolor and malassezia folliculitis, but not in those with tinea manus and pedis, tinea corporis or tinea cruris. Conclusions Wood's lamp examination shows a high specificity and sensitivity and is useful in the diagnosis of tinea versicolor and malassezia folliculitis, but seems unapplicable for the diagnosis of tinea manus and pedis, tinea corporis or tinea cruris.

Photoluminescence of Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 under vacuum ultraviolet excitation

Novel Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 phosphors were synthesized by solid-state reaction and their photoluminescence properties in vacuum ultraviolet region were investigated for the first time. It can be observed from the excitation spectra that the host-related absorption band is located around 170 nm, and it overlaps the O 2− → Tb 3+ charge transfer band of Ca 8MgGd(PO 4) 7:Tb 3+ around 161 nm and the 3d 5 → 3d 44s transition band of Ca 8MgGd(PO 4) 7:Mn 2+ near 200 nm. The 4f–4f 5d spin-allowed and spin-forbidden transitions of Tb 3+ are verified to be located at 170–250 and 257–271 nm, respectively. Upon 147 nm excitation, the dominant emission peak intensity of the Ca 8MgGd 0.1(PO 4) 7:0.9Tb 3+ phosphor is about 2.7 times stronger than that of the commercial Zn 2SiO 4:Mn 2+ green phosphor, and the brightness of the former with a short decay time of 2.5 ms is about 98% of the latter’s. The Ca 8MgGd(PO 4):Mn 2+ phosphor excited at 147 nm exhibits a deep red emission around 650 nm, which could be attributed to the 4T 1 → 6A 1 transition of Mn 2+, with the CIE index (0.679, 0.321). In a word, the results above indicate that both Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 phosphors could be promising for PDP or Hg-free lamp applications.

Electrospinning-derived Tb2(WO4)3:Eu3+ nanowires: energy transfer and tunable luminescence properties

One-dimensional Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires have been prepared by a combination method of sol-gel process and electrospinning. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. The as-obtained precursor samples present fiber-like morphology with uniform size, and Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires were formed after annealing. Under ultraviolet excitation and low-voltage electron beams excitation into WO(4)(2-) and the f-f transition of Tb(3+), the Tb(2)(WO(4))(3) samples show the characteristic emission of Tb(3+) corresponding to (5)D(4)-(7)F(6, 5, 4, 3) transitions due to an efficient energy transfer from WO(4)(2-) to Tb(3+), while Tb(2)(WO(4))(3):Eu(3+) samples mainly exhibit the characteristic emission of Eu(3+) corresponding to (5)D(0)-(7)F(0, 1, 2) transitions due to an energy transfer occurs from WO(4)(2-) and Tb(3+) to Eu(3+). The increase of Eu(3+) concentration leads to the increase of the energy transfer efficiency from Tb(3+) to Eu(3+). The PL color of Tb(2)(WO(4))(3):x mol% Eu(3+) phosphors can be tuned from green to red easily by changing the doping concentration (x) of Eu(3+), making the materials have potential applications in fluorescent lamps and color display fields.

Thermally stable green Ba_3Y(PO_4)_3:Ce^3+,Tb^3+ and red Ca_3Y(AlO)_3(BO_3)_4:Eu^3+ phosphors for white-light fluorescent lamps

A class of thermal stable of green-emitting phosphors Ba(3)Y(PO(4))(3):Ce(3+),Tb(3+) (BYP:Ce(3+),Tb(3+)) and red-emitting phosphors Ca(3)Y(AlO)(3)(BO(3))(4):Eu(3+) (CYAB:Eu(3+)) for white-light fluorescent lamps were synthesized by high temperature solid-state reaction. We observed a decay of only 3% at 150 °C for BYP:0.25Ce3+,0.25Tb3+ (3% for LaPO4:Ce(3+),Tb(3+)), and a decay of 4% for CYAB:0.5Eu(3+) (7% for Y(2)O(3):Eu(3+), 24% for Y(2)O(2)S:Eu(3+)). The emission intensity of composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) is 70% of that of commercial LaPO(4):Ce(3+),Tb(3+) phosphors, and the CIE chromaticity coordinates are found to be (0.323, 0.534). The emission intensity of Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) is 70% and 83% of those of Y(2)O(3):Eu(3+) and Y(2)O(2)S:Eu(3+) phosphors, respectively, and the CIE chromaticity coordinates are redder (0.652, 0.342) than those of Y(2)O(3):Eu(3+) (0.645, 0.347) and Y(2)O(2)S:Eu(3+) (0.647, 0.343). A white-light fluorescent lamp is fabricated using composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) and Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) phosphors and matching blue-emitting phosphors. The results indicate that the quality of the brightness and color reproduction is suitable for application in shortwave UV fluorescent lamps. The white-light fluorescent lamp displays CIE chromaticity coordinates of x = 0.33, y = 0.35, a warm white light with a correlated color temperature of 5646 K, and a color-rendering index of Ra = 70.

Intense violet-blue-emitting Ba_2AlB_4O_9Cl:Eu^2+ phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes

We synthesized a violet-blue phosphor Ba(2)AlB(4)O(9)Cl:Eu(2+) with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f(7)-4f(6)d(1) transitions of Eu(2+). The phosphors with different Eu(2+) concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390nm] excitation. The optimum concentration of Eu(2+) in Ba(2)AlB(4)O(9)Cl:Eu(2+) is determined to be 6mol.%. The luminous efficiency was found to be 8.1lm/W for the violet-blue fluorescent lamp and 3.2lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba(2)AlB(4)O(9)Cl:Eu(2+) would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator.

Novel Dy3+-doped Ca2Gd8(SiO4)6O2 white light phosphors for Hg-free lamps application

Abstract The luminescent properties of Ca2Gd8(1−x)(SiO4)6O2:xDy3+ (1% ≤ x ≤ 5%) powder crystals with oxyapatite structure were investigated under vacuum ultraviolet excitation. In the excitation spectrum, the peaks at 166 nm and 191 nm of the vacuum ultraviolet region can be assigned to the O2− → Gd3+, and O2− → Dy3+ charge transfer band respectively, which is consistent with the theoretical calculated value using Jφrgensen's empirical formula. While the peaks at 183 nm and 289 nm are attributed to the f–d spin-allowed transitions and the f–d spin-forbidden transitions of Dy3+ in the host lattice with Dorenbos's expression. According to the emission spectra, all the samples exhibited excellent white emission under 172 nm excitation and the best calculated chromaticity coordinate was 0.335, 0.338, which indicates that the Ca2Gd8(SiO4)6O2:Dy3+ phosphor could be considered as a potential candidate for Hg-free lamps application.

Luminescent properties of Tb 3+ activated GdTaO 4 with M and M′ type structure under UV–VUV excitation

The photoluminescence of Tb 3+ doped M and M′ type gadolinium orthotantalate Gd 1− x Tb x TaO 4 (0.01≤ x≤0.20) was investigated under ultraviolet and vacuum ultraviolet excitation. For the samples of Gd 1− x Tb x TaO 4 with different crystallographic structures, emission spectra were the same in addition to intensity; the optimal concentration for Tb 3+ was about 10 mol % in M type Gd 1− x Tb x TaO 4 but 5 mol % in M′ type Gd 1− x Tb x TaO 4. These differences could be corresponding with the difference in structures. In addition, compared to commercial Zn 2SiO 4: Mn 2+, the integrated intensity of M and M′ type GdTaO 4: Tb 3+ could reach 67% and 85%, respectively, of that at 147 nm excitation, which indicates that GdTaO 4: Tb 3+ would be a promising vacuum ultraviolet phosphor for application in PDP and Hg-free lamp.

Novel Red-Emitting Phosphor Ca9Y(PO4)7:Ce3+,Mn2+ with Energy Transfer for Fluorescent Lamp Application

A series of new luminescent emission-tunable phosphors Ca(9)Y(PO(4))(7):zCe(3+),xMn(2+) have been synthesized by a high-temperature solid-state reaction. We report a broad deep red-emitting composition-optimized phosphor (Ca(0.9))(9)Y(0.85)(PO(4))(7):0.15Ce(3+),0.1Mn(2+), which has been found to be feasible for the application in fluorescent lamps. The Commission Internationale de I'Eclairage (CIE) chromaticity coordinates measured for the phosphor were (0.68, 0.29), and those for fluorescent lamps with and without a 600 nm filter were found to be (0.67, 0.29) and (0.54, 0.32), respectively. The Ca(9)Y(PO(4))(7):Ce(3+),Mn(2+) phosphor showed two emission bands under 254 nm excitation: the one observed at 366 nm was attributed to Ce(3+) ion emission, and the other found at 650 nm was assigned to the emission from Mn(2+) ions. We have shown that the mechanism of energy transfer from Ce(3+) to Mn(2+) was of the resonance type and it occurred via an electric dipole-quadrupole interaction. Furthermore, we have calculated the critical distance for Ce(3+) --> Mn(2+) energy transfer to be 13.45 A by concentration quenching methods.

Synthesis and luminescence of Ca 4YO(BO 3) 3:Eu 3+ for fluorescent lamp application

The red-emitting Ca 4YO(BO 3) 3:Eu 3+ phosphor has been prepared at 1200 °C by the simple solid-state reaction. This preparation temperature is much lower than Y 2O 3:Eu 3+ (1400–1500 °C) for conventional solid-state reaction method. In particular, the complete process to produce high-quality phosphor particles was carried out through the single-step heat treatment of the mixture of corresponding oxide-type metal sources. For this material, the XRD, PL, PL excitation (PLE) and SEM features have also been investigated. The X-ray diffraction data indicate that pure phase of Ca 4YO(BO 3) 3:Eu 3+ can be successfully obtained. Among the different emission transitions 5D 0 → 7F J =0, 1, 2, 3, 4 of this phosphor, one particular transition ( 5D 0 → 7F 2) at 610 nm has been found. Besides carrying out these essential measurements, we have also made an attempt to observe a strong red emission performance displayed by this phosphor for use as coating material on compact fluorescent lamps (CFLs). The results clearly indicate that the life time based on Ca 4YO(BO 3) 3:Eu 3+ was found to be much longer than that using Y 2O 3:Eu 3+. The good performances of the CFLs demonstrate that this phosphor may be suitable for application on short ultraviolet fluorescent lamp.

Self-assembled 3D architectures of lanthanide orthoborate: hydrothermal synthesis and luminescence properties

Nearly monodisperse YBO3 architectures with various shapes have been prepared on a large scale by a facile, effective, and environmentally friendly hydrothermal process using Y(OH)3 as a precursor. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. The shape and size of these as-prepared YBO3 architectures can be tuned effectively by controlling the reaction conditions, such as reaction time, and the molar ratio of H3BO3/Y(OH)3. As a typical morphology, the possible formation mechanism for YBO3 monodisperse flower-like microstructures is presented in detail. To extend this method, other LnBO3 (Ln = Dy, Ho, Er) architectures with well-defined shape and dimensionality can also be achieved by adjusting different rare-earth hydroxides precursors. Under UV excitation and low-voltage electron beam excitation, YBO3: 5 mol % Eu3+ sample exhibits a strong red emission lines of Eu3+ corresponding to 5D0 → 7FJ (J = 0–4) transitions. When doped with 5 mol % Tb3+ ions, the emission lines of Tb3+ corresponding to 5D4 → 7FJ (J = 6, 5, 4, 3) transitions with 5D4 → 7F5 (green emission at 542 nm) being the most prominent group have been observed. This work sheds some light on the design of a well-defined complex nanostructure, and the luminescent properties have potential applications in fluorescent lamps and field emission displays.

Synthesis and optimum luminescence of monodispersed spheres for BaWO4-based green phosphors with doping of Tb3+

Monodispersed spheres for Tb3+-doped BaWO4 (BWO:Tb) phosphors were prepared by a hydrothermal method. X-ray diffraction (XRD) and field-emission scanning electron microscopy were used to characterize the resulting samples. Emission and excitation spectra were studied using xenon excited spectroscopic experiments at room temperature. Because 12 at% BWO:Tb phosphor exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO4:Ce,Tb), it is considered to be a new promising green phosphor for fluorescent lamps application.

A novel Dy3+-doped GdPO4 white-light phosphors under vacuum ultraviolet excitation for Hg-free lamps application

Novel Dy3+-doped GdPO4 white light phosphors with monoclinic system were successfully synthesised by hydrothermal method at 240 °C. This paper investigates the luminescence properties of white-light Gd1–xPO4:xDy3+ under vacuum ultraviolet (VUV) excitation. The strong absorption at around 147 nm in excitation spectrum energy can be transferred to the energy levels of Dy3+ ion from the host absorption. Additionally, this white light phosphors are activated by a single Dy3+ ion and with a lower preparation temperature, which tend to decrease the consumption of rare earth resource and energy. Therefore, the luminescence of Gd1-xPO4:xDy3+ under VUV excitation is effective, and proves to be promising in application to mercury-free lamp.

Fabrication and Luminescence Properties of One-Dimensional CaMoO4: Ln3+ (Ln = Eu, Tb, Dy) Nanofibers via Electrospinning Process

One-dimensional CaMoO(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO(4):Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO(4) samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO(4)(2-) groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO(4):Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation. The energy transfer process was further studied by the emission spectra and the kinetic decay curves of Ln(3+) upon excitation into the MoO(4)(2-) groups in the CaMoO(4):x mol % Ln(3+) samples (x = 0-5). Furthermore, the emission colors of CaMoO(4):Ln(3+) nanofibers can be tuned from blue-green to green, yellow, and orange-red easily by changing the doping concentrations (x) of Ln(3+) ions, making the materials have potential applications in fluorescent lamps and field emission displays (FEDs).

Hydrothermal synthesis and photoluminescence of SrWO 4:Tb 3+ novel green phosphor

Tb 3+-doped SrWO 4 phosphors with a scheelite structure have been prepared by hydrothermal reaction. X-ray powder diffraction, field-emission scanning electron microscopy, photoluminescence excitation and emission spectra and decay curve were used to characterize the resulting samples. Scanning electron microscopy image showed that the obtained SrWO 4:Tb 3+ phosphors appeared to be nearly spherical and their sizes ranged from 1 to 3 μm. Photoluminescence spectra indicated the phosphors emitted strong green light centered at 545 nm under ultraviolet light excitation. Because 12 at.% SWO 4:Tb 3+ phosphor exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO 4:Ce,Tb), the excellent luminescence properties make it a new promising green phosphor for fluorescent lamps application.

Hydrothermal synthesis and luminescent properties of Y 2O 3:Tb 3+ and Gd 2O 3:Tb 3+ microrods

One-dimensional (1D) Y 2O 3:Tb 3+ and Gd 2O 3:Tb 3+ microrods have been successfully prepared through a large-scale and facile hydrothermal method followed by a subsequent calcination process in N 2/H 2 mixed atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectra (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The as-formed products via the hydrothermal process could transform to cubic Y 2O 3:Tb 3+ and Gd 2O 3:Tb 3+ with the same morphology and slight shrinking in size after a postannealing process. Both Y 2O 3:Tb 3+ and Gd 2O 3:Tb 3+ microrods exhibit strong green emission corresponding to 5D 4 → 7F 5 transition (542 nm) of Tb 3+ under UV light excitation (307 and 258 nm, respectively), and low-voltage electron beam excitation (1.5 → 3.5 kV), which have potential applications in fluorescent lamps and field emission displays.

Preparation and Luminescence Properties of Gd2MoO6 : Eu3 + Nanofibers and Nanobelts by Electrospinning

nanofibers and nanobelts have been prepared by a combination method of the sol–gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy, photoluminescence, and low voltage cathodoluminescence as well as kinetic decays were used to characterize the resulting samples. The results of XRD and FTIR indicate that the samples have crystallized at with the monoclinic structure. The SEM and TEM results indicate that the as-formed precursor fibers and belts are uniform and that the as-prepared nanofibers and nanobelts consist of nanoparticles. phosphors show their strong characteristic emission under UV excitation (353 nm) and low voltage electron-beam excitation (3 kV), making the materials have potential applications in fluorescent lamps and field-emission displays.