Cl Phosphors Research Articles

Synthesis and novel emission properties of Bi3+ -doped Ca2 BO3 Cl phosphor for plant cultivation.

In the present work, a series of Bi3+ -activated Ca2 BO3 Cl phosphors was synthesized using the conventional high-temperature solid-state reaction method. The crystal structure of the prepared sample was determined to be monoclinic with space group P21/c. Scanning electron microscopy (SEM) analysis demonstrated the surface morphology with aggregated particles and sizes in the nano range. The presence of vibrational features and their luminescence characteristics were studied using Fourier transform infrared spectroscopy and photoluminescence (PL) techniques, respectively. At the 486 nm excitation wavelength, the PL spectrum revealed a sharp emission centred at 732 nm that was attributed to the 3 P1 →1 S0 transition of Bi3+ . The emission spectra exhibited the highest emission intensity at 0.5mol% Bi3+ ion concentration, beyond this the emission intensity decreased due to the concentration quenching phenomenon attributed to multipolar interaction. The Commission Internationale de l'éclairage coordinates located at (0.7347, 0.2653) confirmed emission in the deep-red region with a colour purity of 99.98%. The obtained outcomes suggested that the reported material may be a promising candidate as a red-emitting phosphor for w-LEDs and plant growth applications.

Luminescence investigation of Sm3+ ,Eu2+ -activated/co-activated Ba2 AlB4 O7 Cl phosphors: novel red to blue colour tuning in chloroborates.

Borochlorate phosphors have shown their worth in modern day lighting over the last few years. Colour tunability of the phosphor is a modern techniques used to obtain white-light-emitting diodes (WLEDs). In the proposed work, Sm3+ ,Eu2+ -activated/co-activated Ba2 AlB4 O7 Cl phosphors were investigated for WLED applications as well as display devices. A convectional solid-state diffusion method was used to synthesize the proposed phosphors. X-ray diffraction (XRD) of the proposed phosphors confirmed the crystalline nature of the sample. Morphological studies on the samples were carried out using scanning electron microscopy analysis. A photoluminescence study of the colour tunable phosphor showed the characteristic peak of Sm3+ together with one broad peak for Eu2+ ions. Red to blue colour tunability was observed in the proposed phosphor with enhancement of Eu2+ ions. All these results showed the worth of this sample in WLED applications as well as in display devices.

Effect of the anion on the luminescence properties of Bi3+-doped X-mayenite (X=O, F, Cl) phosphors

A series of Bi3+-doped X-mayenite (X = O, F, Cl) phosphors was synthesized via the conventional solid-state reaction method. Upon excitation at 325 nm, Bi3+-doped O-mayenite exhibits a single blue emission band peaking at 452 nm, which is assigned to the 3P1→1S0 transitions of Bi3+ ions. For F-mayenite:Bi3+ and Cl-mayenite:Bi3+ phosphors, there is a new dominant ultraviolet emission centered at 375 nm and a weak blue emission. The luminescent dynamical process proves that two emission centers exist in F-mayenite:Bi3+ and Cl-mayenite:Bi3+. Our results confirm that the ultraviolet emission originates from the transitions of Bi3+ with Cl− or F− ions surrounded, and the blue emission corresponds to the transitions of Bi3+ with O2− ions surrounded. In addition, the emission color of Cl-mayenite:Bi3+ can be tuned both by controlling the encaged anions and Bi3+ content. We demonstrate that anion control is a new desirable strategy for photoluminescence tuning.

A novel graphene-based electroluminescent gas sensor for carbon dioxide detection

In this research, we report a new application of alternating-current electroluminescent (AC-EL) devices for carbon dioxide (CO2) detection at room temperature. The EL structure was designed for gas-sensing applications by replacing a dielectric layer with a graphene gas-sensing layer. The graphene-based EL gas sensor was fabricated by screen-printing of a ZnS:Cu,Cl phosphor layer and drop-coating of graphene synthesized by chemical vapor deposition (CVD) process. Optical characterizations confirmed that the graphene-based EL gas sensor showed similar optical properties to a typical AC-EL display device. From gas-sensing results, the AC-EL gas sensor exhibited high response to CO2 in concentration range of 100–1000 ppm at room temperature and high selectivity against NH3, C2H5OH and C7H8. Furthermore, the EL gas sensors offer good repeatability, reproducibility and measurement accuracy. A sensing mechanism of AC-EL gas sensor was explained based on the resistance change of graphene sensing layer via a direct charge transfer process. These results could pave the way to develop a new type of gas sensor based on an EL principle.

Synthesis, structure and luminescent properties of a new white phosphor Ba7(BO3)3(SiO4)Cl:Dy3+ for light-emitting diodes

A new Dy3+ activated Ba7(BO3)3(SiO4)Cl phosphor with complex anionic groups was synthesized by the high temperature solid state reaction technique. The X-ray powder diffraction analysis showed that the phosphors crystallized in polar space group P63mc of the hexagonal system. The excitation and emission spectra, decay curves and chromaticity coordinates were characterized to investigate the photoluminescence properties. The Ba7(BO3)3(SiO4)Cl:Dy3+ phosphors could be effectively excited by UV–visible light from 280 to 500 nm. The emission spectra exhibited three emission bands peaking at 480 (blue light), 576 (yellow light) and 665 nm (red light), which were due to the 4F9/2-6H15/2, 4F9/2-6H13/2 and 4F9/2-6H11/2 transitions of Dy3+, respectively. When Dy3+ concentration exceeded 12 mol%, the concentration quenching occurred. The critical distance between Dy3+ ions was calculated to be about 9.22 Å. In addition, the chromaticity coordinates of the phosphor are (0.33, 0.37), and the point is in the white region.

A Controlled Growth of ZnO Nanostructures on ZnS

ZnO nanostructures were developed on a microsphere of ZnS:Cu,Cl phosphor (ZC) for a potential application to a new light source. The growth mechanisms of these nano-structures are very different from those of previously reported methods due to the difference in the zinc ion source of ZnO on the micro-sphere ZC. In this report, ZnO plays two different roles: provision of a seed site and a zinc ion source during the swelling and hydrothermal reaction. In building nanostructures, nano-wires appeared nano-wires first appeared and played a key role in the growth of seed sites of nano-flowers. Additionally, a significant luminance enhancement in the CL spectrum is observed from the emission of the flowers/ZC apparently caused by secondary excitation due to the emission from ZnO nanoflowers.

Characteristic Properties of Advanced Coil-External Electrodes of Fluorescent Lamps

The coil-EEFL lamps, which are operated with DC driving circuit, have studied. The figure of the merit of the coil-EEFL lamps is the quantum efficiency (ηq) that is given by the emitted visible photons by one moving electron in the FL lamp. The electrons in the FL lamps move on in the superconductive vacuum (R = 0) in the positive column at above room temperature, giving rise to the astronomical ηq = 1013 visible photons (m3.s)-1. Miraculously, the developed coil-EEFL lamps in the parallel connections light up with WDC = 0, without the sacrifice of the illuminance (lm.m-2). Furthermore, the scraped 40 W-HCFL lamps revitalize to the coil-EEFL lamps, promising the operation life longer than 106 hours. The shallow gap between phosphor screen and positive column can be made by side by side arrangement of the low voltage CL phosphor particles and PL phosphor particles. The coil-EEFL lamps in parallel connections may contribute to the Green Energy Projects of UN.

Synthesis and characterization of novel Na15 (SO4 )5 F4 Cl:Ce3+ halosulfate phosphors.

A series of Na15 (SO4 )5 F4 Cl phosphors doped with Ce3+ ions was prepared using the wet chemical method. X-Ray diffraction studies were used to determine their phase formation and purity. Fourier transform infrared spectroscopy effectively identified the chemical bonds present in the molecule. The photoluminescence properties of the as-prepared phosphors were investigated and the Ce3+ ions in these hosts were found to give broadband emission in the UV range. For the thermoluminescence study, phosphors were irradiated with a 5 Gy dose of γ-rays from a 60 Co source. Chen's half-width method was employed to calculate the trapping parameters from the thermoluminescence glow curve. Copyright © 2016 John Wiley & Sons, Ltd.

Zncds:Cu, Al, Cl: A Near Infra-Red Emissive Phosphor for Marking, Coding, and Identification

The availability of near-ultraviolet light and visible light emitting diodes in addition to infrared emitting systems has made the remote excitation of infrared emitting phosphors a practical possibility. Infrared emitting powder phosphors have the potential to meet marking and coding requirements, especially in low light and poor visibility. The advantages of IR emitting powder phosphors are:- 1) That they can easily be deposited by conventional techniques to form large areas, if required, either by simple settling techniques, or by inclusion in a binder suitable for screen or ink-jet printing (the binder must be transparent over the required spectral range). 2) Such deposited powder layers, depending on thickness and particle size etc., can be used in a transmission or reflective mode with suitable UV or visible excitation sources. The ease of fabrication and the wide excitation spectra efficiency of the material facilitate a wide range of potential applications, including the following as preliminary examples: a) For use in coding/marking systems as simple IR sensitive markers. b) For improved marking/detection in conjunction with night vision systems.1 It has been reported that increasing the cadmium concentration in Zn1-xCdxS solid solutions shifted the photoluminescence emission band to longer wavelength because the band gap energy (Eg) decreases with increasing cadmium concentration, from 3.91eV for ZnS to 2.58eV in CdS.2 Werring et al used Zn0.4Cd0.6S:Cu with an emission peak at ~900nm in order to match with the absorption peak of a silicon thyristor for use in an infrared switching device.3 Altering the zinc to cadmium ratio allows fine tuning of the wavelength of the photoluminescent emission band. The aim of this work was to shift the emission peak of the phosphor sufficiently far into the infra-red region so that visible light emission was minimised and the infra-red emission from the phosphor was clearly detectable by night vision systems. Zn1-xCdxS:Cu phosphors with higher cadmium concentrations higher than Zn0.4Cd0.6S:Cu were selected for study with the aim that the increased cadmium concentration would result in the emission band being moved sufficiently far into the near infrared region. Zn1-xCdxS:Cu0.03,Al0.03,Cl and Zn1-xCdxS:Cu0.03,Cl and (where x =0.5-0.9) phosphors were synthesized by an aqueous decomposition method. The photoluminescent (PL) excitation spectra, at 1000nm emission, of Zn1-xCdxS:Cu0.03,Al0.03,Cl (where x =0.5-0.9) phosphors are presented in Figure 1a, and the corresponding PL emission spectra in Figure 1b. For the excitation spectrum of each phosphor (Figure 1a) there was a broad peak at ~365nm, a more intense sharp peak between ~460-505nm which shifted to longer wavelengths with increasing cadmium concentration, and an intense very broad excitation band between ~520nm and ~645nm. The relatively strong excitation band at ~365nm facilitates the use of long wavelength UV lamps and UV emitting LEDs as backlights for the infrared emission panels and broad excitation in the blue region means that these IR emitting phosphors could also be excited by blue light emitting LEDs. Addition of aluminium ions as a co-dopant in these phosphors resulted in a blue shift in emission intensity (Figure 1b) compared to the corresponding Zn1-xCdxS:Cu0.03,Cl phosphors (Figure 1c). The shift to shorter wavelengths was ~70nm for Zn0.5Cd0.5S:Cu0.03,Al0.03,Cl but decreased in intensity with increasing cadmium concentration. The blue shift for Zn0.9Cd0.1S:Cu,Al,Cl was ~30nm. A comparison of the emission brightness of Zn1-xCdxS:Cu0.03,Al0.03,Cl and Zn1-xCdxS:Cu0.03,Cl (where x =0.5-0.9), is presented in Figure 1d. For the phosphors which did not include aluminium as a co-dopant, there was a small increase in emission intensity with increasing cadmium concentrations; this reached a plateau at the highest cadmium concentrations. In contrast, the presence of aluminium resulted in a significant increase in the PL emission intensity at the highest cadmium concentrations. The PL emission peak of Zn0.1Cd0.9S:Cu0.03,Al0.03,Cl was 219% more intense compared to that of Zn0.1Cd0.9S:Cu0.03,Cl. At the higher cadmium concentrations, PL emission which involved Al-Cu donor acceptor pairs resulted in significantly brighter PL emission compared to PL emission from Cl-Cu donor-acceptor pairs. Reference A. Vecht, J. Silver, R. Withnall, and G.R. Fern, DARPA Report, R+D 9350 EE01, (2004)S. Shionoya in Phosphor Handbook, 2nd ed., W.M. Yen, S. Shionoya, and H. Yamamoto, Editors, p256, CRC Press, Boca Raton (2007).N.J. Werring, A. Vecht, and J.W. Fletcher, Brit. J. Appl. Phys. (J. Phys. D), 2, 509-513, (1969). Figure 1. (a) PL excitation spectra, at 1000nm emission of Zn1-xCdxS:Cu0.03,Al0.03,Cl (where x =0.5-0.9) phosphors, (b) normalised PL emission spectra, under 580nm excitation, of Zn1-xCdxS:Cu0.03,Al0.03,Cl (where x =0.5-0.9) phosphors, (c) normalised PL emission spectra, under 580nm excitation, of Zn1-xCdxS:Cu0.03,Cl (where x =0.5-0.9) phosphors and (d) PL emission intensities of Zn1-xCdxS:Cu0.03,Cl phosphors (à) and Zn1-xCdxS:Cu0.03,Al0.03,Cl phosphors (ð) with increasing cadmium concentrations (x). Figure 1

Effect of halohydrocarbon solvents on the dielectric performance of a polymer film and its application to inorganic electroluminescent devices

Polymer films with halohydrocarbon solvents as additive solvents were fabricated to investigate the solvent effect on dielectric performance. Bromobenzene, chlorobenzene (CB), chloroform, and fluorobenzene (FB) were used as halohydrocarbon solvents. The cyanoethyl pullulan (CRS) polymer film with CB had a dielectric constant of 21.5 with a dielectric loss of 0.017 at 100 Hz, which exhibited a 37% increase in dielectric constant compared to the neat CRS polymer film. Increment of the dielectric constant is attributed to the high polarizability of carbon–chlorine bonds originated from CB absorbed in CRS. For the case of the CRS polymer film with FB, the dielectric constant did not increase due to the low polarizability of carbon–fluorine bonds. In order to verify the dielectric performance of the CRS polymer film with CB (CRS/CB), AC-driven inorganic powder electroluminescent (EL) device was fabricated using the green emission ZnS:Cu,Cl phosphor particles. An EL device with CRS/CB polymer film as a dielectric layer exhibited a 37% and 55% increase in luminance and efficiency, respectively compared to that with neat CRS polymer. This increase in EL performance was attributed to the increase of charge carrier density at the interface between the emitting and dielectric layers, resulting in the increased possibility of the charge carrier tunneling into phosphor particles.

Effect of shock wave treatment on luminescence of ZnS:Cu,Cl phosphors

It is shown that shock wave treatment of ZnS:Cu phosphor between synthesis and annealing steps by placing phosphor powder into preservation ampoule and subjecting to the effect of explosion has positive effect on photo- and electroluminescence brightness due to increase of activator (copper) solubility in phosphor matrix and formation of additional ClS–CuZn and ClS–VZn luminescent centers.

Special Arrangement of Phosphor Particles in Screen for Optimization of Illuminance (lm m<sup>-2</sup>) of FL Tubes

The performance of lighted FL tubes is severely influenced by the depth of the gap between phosphor screen on inner glass wall and positive column which is defined by Fvect ≥ Fphos. Fphos is vertical electric field of the surface bound electrons (SBE) on electric insulator in vacuum. The SBE on phosphor particles in the screen of the commercial FL tubes pushes back approaching electrons from phosphor screen to positive column. Naturally, there is the gap between positive column and phosphor screen. The depths of the gap ever study on the lighted FL tubes quantitatively. The depth by the gap by SBE is 3 x 10-3 m that gives rise to the slow build - up curve of illuminance from FL tube. Unexcited Hg atoms in the gap severely control the illuminance (lm m-2) of FL tubes. The reliable FL tubes should have the depth of the gap less than 2 x 10-4 m. The formation of the narrow gap requires the special arrangement of (a) the low voltage CL phosphor particles and (b) PL phosphor particles side by side. The coil-EEFL tubes in the narrow gap allow the Ar gas pressures (>7 x 103 Pa) for the high illuminance (>103 lm m-2) with nearly zero power consumption by the DC operation.

Tb3+ Doped Sr2(BO3)Cl Green Emitting Phosphor For Solid State Lighting

In this paper we present luminescence results on Tb 3+ doped Sr2(BO3)Cl green phosphor. The vibrational properties of Sr2(BO3)Cl phosphor was studied by Fourier transform infrared spectroscopy. Photoluminescence studies have been carried out to understand the mechanism of excitation and the corresponding emission in the as prepared phosphor. As the Tb 3+ ion is commonly used as an activator for the green emission, the excitation and emission spectra indicate that this phosphor can be effectively excited by 380 nm, to exhibit bright green emission centered at 546 nm corresponding to the f→f transition of Tb 3 + ions. Copyright © 2014 VBRI press.

Study of luminescence and effect of Dy3+ on NaMgSO4 Cl:Ce chlorosulphate phosphor.

Chlorosulphate NaMgSO4 Cl phosphor doped with Ce(3+) and co-doped by Dy(3+) prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce(3+) shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce(3+) → Dy(3+) ions. Dy(3+) emission at 485 nm and 576 nm is due to (4) F9/2 → (6) H15/2 and (4) F9/2 → (6) H13/2 transitions of Dy(3+) ion respectively. The TL glow curves of NaMgSO4 Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ-rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247-312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ-ray dose. There is still scope for higher doses of γ-radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies.

A Highly Efficient White Light (Sr3,Ca,Ba)(PO4)3Cl:Eu2+, Tb3+, Mn2+ Phosphor via Dual Energy Transfers for White Light-Emitting Diodes

A series of single-phased (Sr3-x,Ca1-y-z,Ba)(PO4)3Cl (SCBPO_Cl):xEu(2+), yTb(3+), zMn(2+) phosphors were synthesized by high-temperature solid-state reaction, and luminescent properties of these phosphors were investigated by means of photoluminescence and microcathode luminescence (μ-CL). Under UV excitation, white-light emission was obtained from triactivated SCBPO_Cl phosphors via combining three emission bands centered at 450, 543, and 570 nm contributed by Eu(2+), Tb(3+), and Mn(2+), respectively. White-light emission with the three emission bands is further demonstrated in the fluorescence microscope images, CL spectrum, and μ-CL mappings, which strongly confirm that the luminescence distribution of as-prepared SCBPO_Cl:xEu(2+), yTb(3+), zMn(2+) phosphors is very homogeneous. Both spectral overlapping and lifetime decay analyses suggest that dual energy transfers, that is, Eu(2+)→Tb(3+) and Eu(2+)→Mn(2+), play key roles in obtaining the white emission. The International Commission on Illumination value of white emission as well as luminescence quantum yield (51.2-81.4%) can be tuned by precisely controlling the content of Eu(2+), Tb(3+), and Mn(2+). These results suggest that this single-phased SCBPO_Cl:xEu(2+), yTb(3+), zMn(2+) phosphor may have a potential application as a near-UV convertible white-light emission phosphor for phosphor-converted white light-emitting diode.

High performance of the organic–inorganic powder electroluminescence device with high color-rendering capability using the multilayer

An AC-driven organic–inorganic hybrid powder electroluminescence (EL) device was made to investigate the effect of organic dye on EL performance. The bluish green emitting-ZnS:Cu,Cl phosphor and coumarin 6 (and DCJTB) were used as emitting material and organic dyes (color converting material), respectively. In order to convert an emission spectrum effectively, an EL device composed of the Al/dielectric layer/composite emitting layer (phosphor–coumarin 6)/red-color-filter layer (DCJTB)/indium tin oxide electrode was prepared using the top-emission structure. At 150V and 10kHz, the organic–inorganic hybrid EL device had a luminance of 780cd/m2 and a color coordinate of (0.65, 0.33) in Commission International de I’Eclairage. The blue emission which originated from ZnS:Cu,Cl at 10kHz was converted into the green emission by coumarin 6. Then, this green emission was converted into red by DCJTB. The high EL intensity and high color-rendering capability were attributed to the color conversion.

Lyoluminescence properties of γ-irradiated and Dy 3+ activated (K0.5 Na0.5)Cl phosphors for accidental radiation dosimetry

The lyoluminescence (LL) properties of γ-irradiated and Dy 3+ activated (K0.5Na0.5)Cl phosphors are reported in this paper. Samples were synthesised by the wet-chemical method. LL characteristics of the phosphor have been recorded for different γ-doses. Single isolated LL peak is observed, which indicates that only one type of luminescence centre is formed during irradiation of prepared materials by γ-ray. Negligible fading is observed in the prepared material. The LL intensity of (K0.5Na0.5)Cl:Dy is found to be dependent on γ-dose and varies linearly with gamma exposures between 0.08–5.00kGy γ-dose. LL intensity is also found to be dependent on concentrations of added Dy3+ impurity in all the samples. The prepared sample may be used for accidental radiation dosimetry.

Local degradation of electroluminescent emission centers in ZnS:Cu,Cl phosphors

ZnS:Cu contains needle-shaped, CuS conducting nano-precipitates along the [111] planes which amplify the applied electric fields near the tips when the field is reversed, enabling AC electroluminescence for ∼50μm thick devices at AC voltages of ∼100V. Unfortunately, the degradation process is poorly understood; previous studies using photodiode measurements were only able to determine the overall device degradation. Here, we analyze many individual emission centers using time-lapse microscope images of several degrading devices. We find that most of the individual emission centers have large, sudden, discrete drops in luminosity and many have a luminosity that actually increases significantly, minutes to hours after a drop. This suggests that there are two primary degradation mechanisms: gradual multi-step diffusion of single-atom trap states away from the high-field region (causing the gradual decrease in luminosity) and the sudden break-up and reformation of complex trap states within the high field region (causing the sudden decreases and increases, respectively).

Mechanoluminescence characterizations in γ-irradiated and Dy3+ activated (K0.5Na0.5)Cl phosphor for accidental radiation dosimetry

The mechanoluminescence of γ-irradiated powder of (K0.5Na0.5)Cl:Dy3+ (0.05–0.5mol%) phosphor is reported. The variation of mechanoluminescence peak intensity with γ-dose and with different concentration of Dy3+ ions doped in (K0.5Na0.5)Cl are studied and compared with thermoluminescence characterization. The variation of peak mechanoluminescence intensity of (K0.5Na0.5)Cl:Dy3+ (0.1mol%) with different γ-ray dose is found to be linear up to 5kGy exposure dose and minimum fading in peak height is observed.

Dy3+and Mn2+ emission in fluoride‐ and chloride‐based Na3(SO4)X (X = F or Cl) phosphors

In the present study, Na3 (SO4)X (X = F or Cl) halosulphate phosphors have been synthesized by the solid-state diffusion method. The phase formation of the compounds Na3 (SO4)F and Na3 (SO4)Cl were confirmed by X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na3 (SO4)F:Ce3+ and Na3 (SO4)Cl:Ce3+ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light and presents a dominant luminescence band centred at 341 nm for Ce3+, which is responsible for energy transfer to Dy3+ and Mn2+ ions. The efficient Ce3+ → Dy3+ energy transfer in Na3 (SO4)F and Na3 (SO4)Cl under UV wavelength was observed due to 4 F(9/2) to 6H(15/2) and 6H(13/2) level, while Ce3+ → Mn2+ was observed due to (4) T1 state to (6) A1 . The purpose of the present study is to develop and understanding the photoluminescence properties of Ce3+ -, Dy3+ - and Mn2+ -doped fluoride and chloride Na3 (SO4)X (X = F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc.