Aluminate Phosphors Research Articles

Preparation of photoluminescent and photochromic smart glass window using sol-gel technique and lanthanides-activated aluminate phosphor

Long-persistent photoluminescent and photochromic glass material capable of changing color under UV irradiation has been produced. With the simple immobilization of alkaline earth aluminate nanoparticles, a photoluminescent translucent glass has been created by the sol-gel method. The glass substrates were shown to change color to green under UV light, as demonstrated by CIE Lab screening. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to study both morphology and composition of the phosphor nanoparticles. On the other hand, the morphologies and chemical contents of the photoluminescent glass samples were examined using scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and X-ray fluorescence (XRF). The mechanical behavior of the prepared luminescent glasses was studied to show better resistance to scratching in comparison to the phosphor-free glass. Aside from that, the spectrum characteristics of photoluminescence excitation and emission were examined in depth. The luminescent glass substrates had two emission intensities of 427 and 522 nm monitored upon excitation at 371 nm. Samples of luminescent glass with lower phosphor levels had rapid reversibility of photochromism, whereas those with greater phosphor contents underwent long-lasting luminosity, similar to that of a flashlight that might substitute for electrical power. Results demonstrated that the photoluminescence colorless glass substrates have improved hydrophobicity and UV shielding.

Immobilization of lanthanide doped aluminate phosphor onto recycled polyester toward the development of long-persistent photoluminescence smart window.

Smart window can be defined as switchable material whose light transmission is altered upon exposure to light, voltage, or heat. However, smart windows are usually produced from expensive and breakable glass materials. Herein, transparent smart window with long-persistent phosphorescence, high optical transmittance, ultraviolet (UV) protection, rigid, high photostability and durability, an d superhydrophobicity was developed from recycled polyester (PET). Recycled polyester waste (RBW) was simply immobilized with different ratios of lanthanide-doped aluminate nanoparticles (LdAN) to provide a long-persistent phosphorescent polyester smart window (LdAN@PET) with an abili ty to persist emitting light for extended time periods. The solid-state high temperature technique was used to prepare lanthanide-doped aluminate (LdA) micro-scale powder. Then, the top-down technique was applied to afford the corresponding LdAN. Recycled shredded recycled polyester bottles were charged into a hot bath to provide a clear plastic shred bulk, which was then well-mixed with LdAN and drop-casted to provide long-persistent luminescent smart window. In order to improve the phosphor dispersion in the PET bulk, LdAN was synthesized in the nanoparticle form which was characterized utilizing transmission electron microscopy (TEM). For better preparation of translucent smart window of long-persistent phosphorescent polyester, LdAN must be homogeneously dispersed in the PET matrix without agglomeration. The morphology and chemical composition were studied by Fourier-transform infrared (FTIR) spectra), X-ray fluorescence (XRF) analysis, scanning electron microscopy (SEM), and energy-dispersion X-ray spectroscopy (EDX). In addition, spectral profiles of excitation and emission, and decay and lifetime were used to better understand the photoluminescence properties. The hardness properties were also investigated. The developed phosphorescent transparent polyester smart window demonstrated a color switch to intense green underneath UV irradiation and greenish-yellow under darkness as verified by CIELab color parameters. The afterglow polyester smart window showed an absorption wavelength at 365 nm and two phosphorescence intensities at 442 and 512 nm. An enhanced UV protection, photostability and hydrophobic activity were detected. The luminescent polyester substrates with lower LdAN ratios demonstrated rapid and reversible fluorescent photochromic activity beneath the UV light. The luminescent polyester substrates with higher LdAN contents displayed long-persistent phosphorescence afterglow. The current strategy can be simply applied for the production of smart windows, low thickness anti-counterfeiting films and warning signs.

SrAl2O4 crystallite embedded inorganic medium with super-long persistent luminescence, thermoluminescence, and photostimulable luminescence for smart optical information storage

As a leader of long persistent luminescence (LPL) materials, the optical properties of aluminate phosphor have remained unsurpassed for many years. As a powder material, its practical application will always be limited to the field of security signs. In this paper, the SrAl 2 O 4 : Eu 2 + , Dy 3 + inorganic solid material with comparable LPL properties to powder materials was obtained. The crystallization mechanism and crystallite micro-morphology of inorganic glass materials have been studied, and a new opinion is put forward that the large-size SrAl 2 O 4 crystallites in the glass matrix are stacked by rod-shaped crystals arranged in a regular direction. In addition, the SrAl 2 O 4 : Eu 2 + , Dy 3 + glass obtained cannot only collect high-energy photons but also is sensitive to low-energy sunlight. The results show that the material exhibits superior performance in LPL, thermoluminescence, and photostimulable luminescence. Based on this property, a new application of this material in the field of information storage was explored. This paper has a certain reference value for the development and application of aluminate LPL materials in the field of smart optical information storage.

Preparation of flame-retardant, hydrophobic, ultraviolet protective, and luminescent transparent wood.

Transparent wood with multifunctional properties has recently attracted more attention as an efficient building product. Here, we describe the development of transparent wood with long-persistent phosphorescence, tough surface, high durability, photostability, and reversibility without fatigue, and with ultraviolet shielding, superhydrophobicity, and flame-retardant activity. This long-persistent phosphorescent, or glow-in-the-dark, smart wood exhibited an ability to continue emitting light for prolonged periods of time. The photoluminescent translucent wooden substrate was prepared by immobilizing lignin-modulated wooden bulk with an admixture of methylmethacrylate (MMA), ammonium polyphosphate (APP), and lanthanide-doped strontium aluminate (LSA; SrAl2 O4 :Eu2+ ,Dy3+ ) phosphor nanoparticles. The photoluminescent transparent wood displayed a colour switch from colourless to bright white beneath ultraviolet (UV) light and greenish-yellow in the dark as reported by Commission Internationale de l'Éclairage laboratory colorimetric space coordinates. The generated phosphorescent wooden substrates demonstrated an absorbance band at 365 nm and an emission band at 516 nm. The phosphorescent transparent wood was improved flame-retardant properties, ultraviolet shielding, and superhydrophobic properties, as well as a reversible long-persistent phosphorescent responsiveness to UV light without fatigue. The current approach demonstrated a potential large-scale production strategy for multifunctional transparent wooden substrates for a range of applications such as smart windows, gentle indoor and outdoor lighting, and safety directional signs in buildings.

Photocatalytic Reaction Properties of TiO₂-Supported on the Long Lasting Phosphor: Sr₄Al14O25:Eu2+,Dy3.

The TiO₂/Sr4Al14O25:Eu2+,Dy3+ photocatalytic composite was prepared by depositing the nano-crystalline titanium dioxide layer on the long-lasting phosphor substrate of strontium aluminate, using a low-pressure chemical vapor deposition (LP-CVD). The photocatalysis characteristic was studied by examining the photodegradation of benzene (C6H6) gas under UV, visible light illumination, and in the darkness. The photocatalytic composite of TiO₂-deposited Sr₄Al14O25:Eu2+,Dy3+ showed an active photocatalytic reactivity under UV-light as well as visible-light illumination. The mechanism of the photocatalysis reaction for the TiO₂-deposited strontium aluminate phosphor composite was interpreted in point of the energy band structure and phosphorescent emission. The coupling of nanocrystalline TiO₂ with the strontium aluminate phosphor might result in an energy band bending at the interface of TiO₂/Sr₄Al14O25:Eu2+,Dy3+, making the titanium dioxide at the junction to be photo-reactive even in a visible wavelength region. In addition, the depth profile of Auger electron spectroscopy (AES) confirmed a possible formation of oxygen vacancies at the interface between TiO₂ and Sr₄Al14O25:Eu2+,Dy3+. Then, oxygen defects create extra electrons which may excited subsequently to the conduction band and participate in a photocatalytic reaction, resulting in an enhancement of the photodecomposition of benzene. The LP-CVD TiO₂-strontium aluminate phosphor was also photoactive in the darkness because of light emission from the long lasting phosphor. Also, the TiO₂-deposited Sr₄Al14O25:Eu2+,Dy3+ long lasting phosphor was analyzed by a XRD (X-ray diffraction), TEM (transmission electron microscopy), UV/visible spectroscopy and AES.

Combustion Synthesis of Some Cr3+-Activated Aluminate Phosphors

Combustion Synthesis of Some Cr3+-Activated Aluminate Phosphors

Bright yellow-emitting long persistent luminescence from Mn2+-activated strontium aluminate phosphor

We developed bright yellow-emitting long persistent luminescence (LPL) materials Sr4Al14O25:Mn2+ and Sr4Al14O25:Mn2+,N (N = Zr4+, Ho3+, Er3+) by high temperature solid–state reaction. The addition of Zr4+, Ho3+ and Er3+ can regulate trap distributions and improve energy storage ability of the materials. The LPL performance of SAO:Mn2+,Ho3+ is optimal, considering LPL intensity and duration time. Bright LPL of SAO:Mn2+,Ho3+ can be observed for 3 h by naked eyes in dark after removing the excitation source. Profiles of LPL spectra are different from those of PL, because the two types of Mn2+ centers do not play equal parts in LPL and photoluminescence (PL). Trap depths of TL peaks centered at 354 K (peak 1) and 455 K (peak 2) are 0.60 and 0.72 eV, respectively. And peak 1 at 354 K is the effective TL peak responsible for LPL. In SAO:Mn2+,Ho3+,Mn2+ ions doped in Al3+ sites serve as emitting centers, and positively charged HoSr· defects are the main effective trap centers. Finally, a feasible LPL mechanism of SAO:Mn2+,Ho3+ was proposed to clarify the generation process of LPL.

Energy efficient microwave-assisted preparation of deep red/near-infrared emitting lithium aluminate and gallate phosphors

The development of impurity doped luminescent materials, or phosphors, have been continuously pursued for a variety of applications nowadays. However, the majority of phosphors undergo time-consuming and energy inefficient preparation, such as conventional high-temperature solid-state reaction (SSR). In the present work, a facile microwave-assisted solid-state (MASS) method is used to prepare a series of transition metal (Mn4+ or Cr3+) doped lithium aluminates and gallates. With a one-step 25-min MASS method, LiAlO2 is obtained in γ phase rather than α phase. Using the same method, followed by a short thermal treatment in air or two-step MASS preparation, inverse spinel LiAl5O8:Mn4+ phosphors with deep-red emission are obtained, while near-infrared emitting LiGa5O8:Cr3+ persistent phosphors are successfully prepared with a 40-min MASS process. Compared to the SSR method, LiGa5O8:Cr3+ achieved by MASS exhibits totally different trap depth and trap distributions, which is evidenced by the temperature dependency of persistent luminescence. The study of the detailed preparation of transition metal doped lithium aluminates and gallates may enable more widespread use of MASS method and facilitate the exploration of new luminescence properties involving defects.

Luminescence Studies of rare-earth Ce3+ and Dy3+ doped SrAl2O4 aluminate phosphors

Luminescence Studies of rare-earth Ce3+ and Dy3+ doped SrAl2O4 aluminate phosphors

Recent Developments in Lanthanide-Doped Alkaline Earth Aluminate Phosphors with Enhanced and Long-Persistent Luminescence.

Lanthanide-activated alkaline earth aluminate phosphors are excellent luminescent materials that are designed to overcome the limitations of conventional sulfide-based phosphors. The increasing research attention on these phosphors over the past decade has led to a drastic improvement in their phosphorescence efficiencies and resulted in a wide variety of phosphorescence colors, which can facilitate applications in various areas. This review article discusses the development of lanthanide-activated alkaline earth aluminate phosphors with a focus on the various synthesis methods, persistent luminescence mechanisms, activator and coactivator effects, and the effects of compositions. Particular attention has been devoted to alkaline earth aluminate phosphors that are extensively used, such as strontium-, calcium-, and barium-based aluminates. The role of lanthanide ions as activators and coactivators in phosphorescence emissions was also emphasized. Finally, we address recent techniques involving nanomaterial engineering that have also produced lanthanide-activated alkaline earth aluminate phosphors with long-persistent luminescence.

Application of Green Solvents for Rare Earth Element Recovery from Aluminate Phosphors

Two processes applying green solvents for recovering rare earth elements (REEs) from different types of aluminate phosphors are demonstrated in this report. For magnesium aluminate-type phosphors, a pretreatment with peroxide calcination was implemented first, and then followed by a supercritical fluid extraction (SFE) process. Supercritical carbon dioxide (sc-CO2) provides an effective and green medium for extracting REEs from dry materials. With the addition of a complex agent, tri-n-butyl phosphate-nitric acid complex, highly efficient and selective extraction of REEs using supercritical carbon dioxide can be achieved. The highest extraction efficiency was 92% for europium from the europium doped barium magnesium aluminate phosphor (BAM), whereas the highest extraction selectivity was more than 99% for the REEs combined from the trichromatic phosphor. On the other hand, for strontium aluminate type phosphors, a direct acid leaching process is suggested. It was found out that acetic acid, which is considerably green, could have high recovery rate for dysprosium (>99%) and europium (~83%) from this strontium aluminate phosphor materials. Nevertheless, both green processes showed promising results and could have high potential for industrial applications.

Mechanoluminescence behaviour on Eu2+/Dy3+ activated SrAl2O4 phosphor

Synthesis of Eu/Dy rare earth doped strontium aluminate phosphor or material with varying concentration of co-dopant (Dy3+) and fixed concentration of dopant (Eu2+) is reported inside the manuscript. Phosphor are prepared and synthesized by using the technique of solid-state reaction in reducing atmosphere and activated charcoal was used to create the atmosphere. Mechanoluminescence pattern were recorded for variable concentration of doping / co-doping ions and it is found with the increment in the concentration of co-dopant up-to 1 mol%, the ML intensity increases and after that the ML intensity decrement occurs due to the phenomenon of concentration quenching. Similarly, for the optimized concentration the ML pattern obtained for gamma – irradiated phosphor and it shows linear response with dose so our study supports the ML dosimeter application to detect the radiation via mechanoluminescence study. The suitable models are compared herein, which are already reported by so many authors.

Photoluminescence Studies of CaAl2O4: EU2+ Blue Phosphors Co-Doped with ND3+ Ion Synthesized by Solid- State Reaction Method

In this work, the polycrystalline CaAl2O4: Eu2+, Nd3+ based blue phosphor was prepared by solid-state reaction method. The rare earth metal ions doped calcium aluminate phosphors have been studied in depth. The high quantum efficiency make them useful for anomalous long phosphorescence, good stability, luminous paints, radiation dosimetry, X-ray imaging, color display, and light emitting diodes. Phase, crystallinity and luminescent properties of the synthesized phosphors were examined by using powder X-ray diffraction (XRD). In the phosphor material, the photoluminescence (PL) spectrum has a broad emission peak of Eu2+ ion in blue region at (λmax = 440 nm) due to the energy transitions between the ground state 4f7 and the excited state 4f65d1 of the Eu2+ ion. This has importance in making the visible phosphor devices from this material. In this study the single dopant phosphors were synthesized; therefore, it is important to improve the long afterglow of the phosphors by codoping. The phosphors of CaAl2O4: Eu2+, Nd3+ had long persistence luminescence. In these phosphors, Eu2+ ions play the role of activators. Whereas Nd3+ ions generate deep traps that lead to the long persistent phosphorescence and act as the co-activators in the phosphors simultaneously. The concentration of Nd3+ ion co-doped has strong influence on the luminescence of phosphor.

Investigation of structural and luminescence properties of BaMgAl10O17:Eu2+ phosphor synthesized using auto combustion method

Abstract In plasma display panel, Eu2+ doped BaMgAl10O17:Eu2+ (BAM: Eu2+) Barium Magnesium Aluminate phosphor have been traditionally adapted as a blue emitting element in many displays owing availability and high (>98%) quantum efficiency. (BAM) phosphor was synthesized in two steps using auto-combustion method followed by sintering in reducing atmosphere. The X-ray diffraction examination confirmed that the crystalline phase of BAM nanophosphor as hexagonal structure. The SEM observation revealed a sharp stone like morphology for the as-prepared nanophosphor. Detailed investigation of photoluminescence has done in the current paper. The results are promising and suggest that the BAM nanophosphor is highly useful in enhancing the color purity in the modern displays.

Thermoluminescence studies of Tm doped nanocrystalline Calcium Aluminate (CaAl2O4:Tm3+)

In this paper we have discussed thermoluminescence (TL) of Tm doped nanocrystalline Calcium aluminate (CaAl2O4:Tm3+) phosphors synthesized by combustion method. Formation and composition of the phosphors have been confirmed by XRD and EDXrespectively. γ- ray and e− beam have been used as source of excitation. The optimal concentration of the activator has been determined by varying the concentration of the activator (Tm). The study is confined to two different aspects of TL study of phosphors i.e. the fundamental physics aspect of the material in term of its key trap parameters namely kinetic energy (E), frequency factor (s) and order of kinetics (b) and its potentiality in possible applications. Computerised Glow Curve Deconvolution (CGCD) technique has been followed to evaluate the trap parameters (E, s and b). The second aspect is being the dose response curve of with the radiations.

Photo and Mechano-luminescence properties of novel Zn1-xEuxAl2-yBayO4 advance blue phosphor

In this work, we have synthesized novel and efficient material Zn0.9655Ba0.0345Al1.9655 O4:Eu0.0345 phosphors by low temperature (500 °C) combustion route, and for better crystallinity, we have annealed with 850–1350 °C in reducing atmosphere of 15% of H2/85% of N2. The crystal structural, element mapping and distribution, morphology, particle homogeneity, and optical properties were measured by various spectroscopic techniques. Photoluminescence (PL) spectra were monitored by excitation and emission (λex. = 492 nm, and λem. = 354 nm) spectra. The PL spectra of phosphors have recorded in order to assess various samples. The PL intensive emission was found at 492 nm due to the Eu (II) ions. The obtained zinc aluminate phosphors have found higher luminescence efficiency due to the high purity and perfect spinel crystallinity of the material. The maximum quantum efficiency was 93.2%, the FWHM was ~64 nm, and the colour purity was 50% have measured for sample S6. With the PL spectrum, we have found good Mechanoluminescence (ML) optical properties of the S6 sample. Therefore, S6 phosphor would be great and useful material for blue pigment, blue LEDs phosphors as well as may be used in various technology in solid-state lighting.

MN and DY doped strontium aluminate’soptical properties- a comparative study

Through sol gel method Mn and Dy doped Strontium aluminate phosphors prepared. The prepared phosphors has been characterized by Powder X-ray diffraction, Scanning electron microscope. Optical properties were carried out by photoluminescence analysis. Photoluminescence studies of the prepared phosphors showed prominent IR emission, green emission and UV emission. To investigate the reaction that took place in the process of sample preparation, simultaneous TG–DSC testing was conducted from room temperature to 1000˚C.

Enhanced luminescence performances of Mn4+-activated Sr4Al14O25 red phosphors by doping with Sc3+ ions

A series of non-rare earth Mn4+-activated strontium aluminate phosphors Sr4Al14O25:Mn4+ co-doped with Sc3+ ions were successfully synthesized by a high-temperature solid-state reaction method. XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc3+ ions. Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light, and a deep red emission centered at 652 nm with a narrow full width at half maximum (FWHM) can be obtained, which is attributed to the transition 2E→4A2 of Mn4+ ions. In addition, the crystal field strength parameter (Dq) and Racah parameters (B, C) and energies of states were calculated based on experimental data. Moreover, the luminous intensity of Sr4Al14-xScxO25:Mn4+ is enhanced and increased by 60% compared with Mn4+ single incorporated sample at x = 0.06. A phenomenon of redshift is observed in the excitation spectrum and discussed systematically. Finally, the mechanism of the positive effects with Sc3+ ions incorporated into lattice is discussed in detail. All the results suggest that the Sr4Al13.94Sc0.06O25:Mn4+ phosphor will become one of the great candidates for backlight of LCD.

Structural and photoluminescence properties of Eu3+ activated ZnAl2O4 orange-red phosphor

Europium doped zinc aluminum oxide (Zn0.93Al2O4:Eu0.07) was successfully prepared by a combustion method at 550 °C, in which urea, glycine, urea–glycine, citric acid, carbohydrazide, tartaric acid, carbohydrazide–glycine, oxalic acid–glycine, and tetraformaltrisazine were used as a fuel (complexing reagents). The structural and morphological properties were measured and elemental analysis carried out using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and energy-dispersive X-ray (EDX), respectively. The photoluminescence (PL) spectra were monitored by excitation spectra (λex. = 378 nm) and emission spectra (λem. = 614 nm), to assess various complexing reagents in which urea was found to be the most efficient for synthesizing ZnAl2O4:Eu3+orange-red phosphor. The discussed zinc aluminate (U-1) phosphor has a higher luminescence intensity at 614 nm. It is concluded, therefore, that the ZnAl2O4:Eu phosphor can be used widely in various solid-state lighting as an orange-red phosphor.

Unusual Red-Shift and Enhanced Photoluminescence of BaMgAl10O17:Eu2+ Phosphor Under Ultraviolet A Excitation for Modern Lighting Systems.

An unconventional red-shift but enhanced photoluminescence (PL) under ultraviolet A (UV-A) irradiation of Eu2+ doped Barium Magnesium Aluminate (BAM) phosphor prepared in both bulk and nanoforms useful for modern lighting applications has been presented. The solid-state reaction and solution combustion approaches were used for the preparation of phosphors with post-annealing step in reduced atmosphere. A significant broad blue-green (˜500 nm) PL associated with the transition of Eu2+ from 4f6 5d1 excited state to the 4f7 ground state has been observed. The observed shifts and PL intensities were found to be extremely reliant on the thermal processing parameters during the synthesis of phosphor/nanophosphormaterials. It's also important to note that the size of the phosphor particles have significant role in defining the red-shift of PL due to quantum confinement effect. Detailed structural and morphological characterizations were also done in this paper. The results are promising and suggest that the BAM phosphor is highly desirable for enhancing the brightness levels in modern lighting and display systems.