Composite Phosphor Research Articles

Effects of argon sintering atmosphere on luminescence characteristics of Ca6BaP4O17:Sm3+ phosphors

In this paper, Ca6BaP4O17:Sm3+ and Li+ co-doped Ca6BaP4O17:Sm3+ phosphors were synthesized in air and argon atmospheres using a solid-state reaction method. The phosphor morphologies and crystal structure were studied using scanning electron microscopy and X-ray diffraction, respectively. The emission and absorption characteristics were investigated using photoluminescence emission spectroscopy and diffuse reflectance spectroscopy. The surface states and composition of phosphor were investigated using X-ray photoelectron spectroscopy. The emission integrated intensities of the phosphors sintered in an argon atmosphere increased 3.5 fold than the ones sintered in air atmosphere, with Li+ ions becoming embedded in the lattice of the Ca6BaP4O17:Sm3+ phosphor. This occurs because there are fewer defect/oxygen vacancies and less of the secondary phase forms, leading to better Sm3+ emission. The results suggest that sintering a mixture of the raw materials of a phosphor in an argon atmosphere is a good approach for synthesizing Ca6BaP4O17:Sm3+ phosphor powders. The color purity and CIE values of an optimized phosphor sample sintered in an argon atmosphere with an Li+ ion compensator were calculated to be ~ 99.6% and (0.612,0.386) in the orange–red region under 405-nm excitation, respectively. Moreover, the solid solubility of Sm3+ ions in the Ca6BaP4O17 host can be enhanced by using an argon atmosphere in the synthesis process.

Correction: Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties.

Correction for 'Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties' by Guo-Hui Pan, Jiahua Zhang et al., Nanoscale, 2018, DOI: 10.1039/c8nr07360k.

Wind Driving Triboluminescence Technology: A Physical Agriculture Method of Pest Insects Control without Pesticides†

Some of triboluminescence materials have the property of shortwave light emission, which is possible to make them being used as the light resource of pest-insects phototaxis trapping. The inorganic composite phosphors Sr2MgSi2O7:Ce and organic composite phosphor Mn-PMBB are tested to have the violet-blue spectrum and green spectrum glowing respectively; Their vertical axis wind driving triboluminescence unit is designed and fabricated on the basis of squirrel cage structure friction pair with multi-glass bars against on the cylindrical phosphor. The persistant wind driving tribo-luminescence is obtained in the experiment of wind driving triboluminescence unit. Further the triboplasma of N2 and N2- Ar gases closed in the quartz tube is researched by means of PTFE elctret on quartz tube friction pair, and a high intensity triboplasma light emission with more than 50000 counts is obtained in the span of 310-420nm spectrum that supplies a more suitable shortwave spectrum of phototaxis trapping pest insects. The annular quartz glass tube is designed to constitute PTFE against on quartz friction pair; The triboplasma emission device is fabricated utilizing three stacking layer structure of PTFE-anuular quartz tube friction pairs, and the S-type vertical shaft wind tuebine is used to form the wind driving triboplasma emission unit. The violet-blue emission spectrum of N2-Ar gas troboplasma is obtained in the test of vertical wind driving triboplasma unit.

Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties.

The most common yellow phosphor for wLEDs, Y3Al5O12:Ce3+ (YAG:Ce3+), suffers from a deficiency of red in its spectral content of light. In this paper, a new strategy is provided to tailor the Ce3+ spectral profile through surface-located dye molecules of ATTO-Rho101, which feature intense, broad absorption in the green-yellow spectral region of Ce3+ emission as well as bright red emission. Sphere-shaped and highly dispersed micrometer and nanometer-sized YAG:Ce3+ (micro/nano-YAG:Ce3+) was synthesized through a modified solvothermal method. Surface SiO2 coating and simultaneous dye embedding were performed on the solvothermally derived YAG:Ce3+, heat-treated micro-YAG:Ce3+ and commercial phosphors. Efficient radiative transfer/reabsorption from Ce3+ in the inner core of YAG to the dye molecules in the SiO2 outer shell, irrespective of the size of the phosphors, was demonstrated in the accumulated YAG:Ce3+@SiO2 + dye powder upon blue light excitation; this enhanced its red emission. Fluorescence microscopy was demonstrated to be a powerful tool to identify the reabsorption phenomenon of the powdered materials. Packaging the heat-treated micro-YAG:Ce3+@SiO2 + dye phosphors on blue LED chips yielded a warm wLED (Ra∼ 93), but an Ra of only ∼79 was obtained for the wLED with commercial YAG:Ce3+@(SiO2 + dye)5 due to the low concentration of phosphors dispersed in the epoxy resin and the resulting decreased reabsorption by dye molecules. Surface-protonated amine species were found to induce Ce3+→ Ce4+ oxidation upon activation by heating or photoirradiation and then quench the photoluminescence (PL) of micro-YAG:Ce3+ even after surface modification by SiO2, YAG or being embedded in an epoxy resin matrix. High calcination temperatures greatly improved the PL stability of micro-YAG:Ce3+ through the removal of surface-capped species. The dye in the silica matrix showed high stability against heating and irradiation due to the so-called "caging effects"; however, decreased photo-stability was found in commercial YAG:Ce3+@(SiO2 + dye)5 due to the incomplete and/or loose SiO2 layer grown during multiple surface modifications.

Photoluminescence properties of a double perovskite tungstate based red-emitting phosphor NaLaMgWO6:Sm3+

In this work, the conventional solid-state method was applied to synthesize a series of red-emitting NaLaMgWO6:Sm3+ phosphors. The crystal structure, phase purity, morphology, particle size distribution as well as elemental composition of the as-prepared phosphors were investigated carefully with the aid of XRD, SEM, EDS, FT-IR analyses, indicating the high-purity and micron-sized NaLaMgWO6:Sm3+ phosphors with monoclinic structure were prepared successfully. The spectroscopic properties of Sm3+ in NaLaMgWO6 host including UV–vis diffuse reflection spectrum, photoluminescence excitation and emission spectra, decay curves, chromaticity coordinates and internal quantum efficiency were investigated in detail. Upon excitation with UV (290nm) and n-UV (406nm), NaLaMgWO6:Sm3+ phosphor presented red emission corresponding to the 4G5/2→6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+, in which the hypersensitive electronic dipole transition 4G5/2→6H9/2 (645nm) was with the strongest emission intensity because Sm3+ ions were located at a lattice site with anti-inversion symmetry. The optimal concentration of Sm3+ was different for the given excitation wavelength such as 290nm and 406nm, which was interpreted by the extra effect of the energy transfer from W6+-O2- group to Sm3+. The decay lifetime for 4G5/2→6H9/2 transition of Sm3+ was very short (< 1ms) and decreased with the increasing Sm3+ concentration. The present investigation indicates that NaLaMgWO6:Sm3+ phosphor could be a potential red component for application in w-LEDs.

Nearly pure NIR to NIR upconversion luminescence in Tm3+, Yb3+ co-doped ZnO-TiO2 composite phosphor powder

Tm3+ and Yb3+ co-doped ZnO-TiO2 composite system were successfully synthesized via powder-solution mixing method and their upconversion (UC) luminescence characteristics were studied as a function of various ZnO/TiO2 mixing ratios and dopant concentrations under 980 nm laser excitation. The XRD patterns showed that the product fired at 1300 °C consisted of four phases, Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Tm3+ and/or Yb3+). The NIR emission centered at 795 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 3H4 → 3H6 transition of Tm3+ ion. The NIR emission intensity of the products was varied by changing ZnO-TiO2 mixing ratios, and Tm3+ and Yb3+ concentrations. The simple chemical formula equations, for interpreting the site preference of Tm3+ and Yb3+ ions in the host crystal matrix, were originated by considering the host crystal structure, its crystal arrangement, and the effect of Tm3+ and Yb3+ ions to the changes in lattice parameters of host crystal. The 1ZnO:1TiO2 (in mole) doped with 0.125 mol% Tm3+, 15 mol% Yb3+ fired at 1300 °C for 1 h was the best condition that displayed highest NIR emission intensity. The possible UC mechanism was suggested and discussed in detail.

Erasing the Glow in the Dark: Controlling the Trap and Release of Electrons in Phosphorescent Materials

Common phosphors found in readily available glow-in-the-dark products include transition-metal-doped zinc sulfide and transition-metal-doped strontium aluminate compounds. Phosphorescence of these materials is initiated by light with energies that are specific to each phosphor composition. In many cases, the phosphorescence of these materials can also be darkened by further excitation with light that has lower energy than the minimum energy required to produce the initial glow. The visible darkening of the phosphor material produces an effect akin to an “off switch” or “eraser” for the emitted light. The light excitation to produce the phosphorescence and the darkening can be produced by either coherent or noncoherent light sources with the proper energies and intensities. Phosphor darkening caused by low-energy light can be used in visually remarkable chemistry demonstrations. Additionally, since the distributions of electrons in the low- and high-energy states in these phosphors can be controlled and ch...

Enhancing Photovoltaic Performance Using Broadband Luminescent Down-Shifting by Combining Multiple Species of Eu-Doped Silicate Phosphors.

This paper demonstrates the application of a broadband luminescent downshifting (LDS) layer with multiple species of europium (Eu)-doped silicate phosphors using spin-on film technique to enhance the photovoltaic efficiency of crystalline silicon solar cells. The surface morphology of the deposited layer was examined using a scanning electron microscope (SEM). The chemical composition of the Eu-doped silicate phosphors was analyzed using energy-dispersive X-ray spectroscopy (EDS). The fluorescence emission of the Eu-doped silicate phosphors was characterized using photoluminescence (PL) measurements at room temperature. We also compared the optical reflectance and external quantum efficiency (EQE) response of cells with combinations of various Eu-doped phosphors species. The cell coated with two species of Eu-doped phosphors achieved a conversion efficiency enhancement (∆η) of 19.39%, far exceeding the ∆η = 15.08% of the cell with one species of Eu-doped phosphors and the ∆η = 8.51% of the reference cell with the same silicate layer without Eu-doped phosphors.

Fabrication of fluorescent dyes supported on porous boron nitride nanosheets and their excellent photoluminescence properties

Fluorescent dyes rhodamine B (RhB) was successfully introduced into the porous boron nitride nanosheets to obtain an effective and rare-earth free light composite conversion materials. X-ray powder diffractions, photoluminescence spectra, etc., were used to investigate the optical performance and thermal stability of these organic-dye-impregnated phosphor composites. The experimental results evidently showed that, compared with the optical properties of RhB in aqueous solution, the composite phosphors possessed more excellent optical performance and higher thermal stability due to their structural defects, surface hydroxyl groups and nanosize pore channel. In addition, the phosphor composites exhibited greatly improved service life and had a broad visible emission wavelengths of 540–680 nm under the 363 nm light excitation. We believe that the reported work should open the way toward the practical application of organic-dye-impregnated phosphor composites in the field of illumination light source.

Facile Two‐Step Synthesis of All‐Inorganic Perovskite CsPbX3 (X = Cl, Br, and I) Zeolite‐Y Composite Phosphors for Potential Backlight Display Application

AbstractRecently developed CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) hold great potential for various applications owing to their superior optical properties, such as tunable emissions, high quantum efficiency, and narrow linewidths. However, poor stability under ambient conditions and spontaneous ion exchange among QDs hinder their application, for example, as phosphors in white‐light‐emitting diodes (WLEDs). Here, a facile two‐step synthesis procedure is reported for luminescent and color‐tunable CsPbX3–zeolite‐Y composite phosphors, where perovskite QDs are encapsulated in the porous zeolite matrix. First zeolite‐Y is infused with Cs+ ions by ion exchange from an aqueous solution and then forms CsPbX3 QDs by diffusion and reaction with an organic solution of PbX2. The zeolite encapsulation reduces degradation and improves the stability of the QDs under strong illumination. A WLED is fabricated using the resulting microscale composites, with Commission Internationale de I'Eclairage (CIE) color coordinates (0.38, 0.37) and achieving 114% of National Television Standards Committee (NTSC) and 85% of the ITU‐R Recommendation BT.2020 (Rec.2020) coverage.

ZnCdS:Cu,Al,Cl: A Near Infra-Red Emissive Family of Phosphors for Marking, Coding, and Identification

Zn1-xCdx:Cu0.03%,Cl (where x = 0.5–0.9) infrared emitting phosphors have been synthesized by an aqueous thermal decomposition method. The aim was to developing infrared emitting phosphors for coding, marking, and identification applications. The phosphors were characterized by, X-ray powder diffraction, scanning electron microscopy and photoluminescence spectroscopy. The emission band at 1000 nm was sufficiently far into the infrared region that visible emission was minimized. Co-doping Zn1-xCdxS:Cu0.03% with Al3+ increased the infrared emission intensity to over twice that of the equivalent Zn0.3Cd0.7S:Cu0.03% phosphor (with no Al3+ ion co-doping), with the highest intensity being found for the phosphor composition Zn0.1Cd0.9S:Cu0.03%, Al0.03%. It is shown herein that the inclusion of Al3+ into the phosphors causes the formation of cells with smaller cell volume, and it is suggested that this is the prerequisite for the improved photoluminescent properties. Finally we have shown herein that these infrared emitting powder phosphors are thus able to meet marking and coding requirements, especially in low light and poor visibility.

Deep red emission enhancement in Mg28Ge10O48:Mn4+ phosphor by Zn substitution

Zinc co-doped Mg28Ge10O48:Mn4+ red phosphors are synthesized by a solid-state method. The effects of zinc on the phosphors have been investigated by varying the stoichiometric proportions of raw materials. Zn concentration affects the phosphor crystallinity, morphology, composition and energy structure. We have carried out the X-ray power diffraction (XRD), Field emission scanning electron microscope (FESEM), energy dispersion spectrum (EDS), element mapping, UV–Vis absorption measurement and X-ray photoelectron spectroscopy (XPS). The phosphorescence enhancement centered at around 660nm is ascribed to 2Eg→4A2g transition of Mn4+. The red emission Intensity of optimized sample is 3.08 and 1.64 times of Zn-free samples and conventional magnesium fluorogermanate phosphors, respectively.

Tuning 2D Light Upconversion Emission by Modulating Phonon Relaxation.

The photonic upconversion in rare earth atoms is widely used to convert "invisible" near infrared photons to "visible" photons with continuous wave light. By using a patterned substrate, upconversion become a route for creating new information-incorporating security codes. The amount of information in the cipher increases in proportion to the number of emission colors as well as the pattern structure. Subsequently, changing the chemical composition of upconversion phosphors on 2 D substrates is required to manufacture information-rich upconversion cryptography. In this study, we exploited temperature-controlled thermal reaction on upconversion films deposited on a quartz substrate to prepare security information codes. Multiple color emission was generated from upconversion films as the result of inserting high-frequency molecular oscillators into the film structures. Fourier-transform infrared (FTIR) and time-resolved study corroborated the mechanism of spectral variation of upconversion films.

Bright red upconversion luminescence from Er3+ and Yb3+ co-doped ZnO-TiO2 composite phosphor powder

Abstract ZnO-TiO2 composites co-doped with Er3+ and Yb3+ ions were successfully synthesized by powder-solution mixing method and their upconversion (UC) luminescence was evaluated. The effect of firing temperature, ZnO/TiO2 mixing ratio, and dopant concentration ranges on structural and UC luminescence properties was investigated. The crystal structure of the product was studied and calculated in detail by means of X-ray diffraction (XRD). Also, the site preference of Er3+ and Yb3+ ions in the host material was considered and analyzed based on XRD results and UC luminescence characteristics. Brightest UC luminescence was observed in the ZnO-TiO2:Er3+,Yb3+ phosphor fired at 1300 °C in which the system consisted of mixed phases; Zn2TiO4, TiO2, RE2Ti2O7 and RE2TiO5 (RE = Er3+ and/or Yb3+). Under the excitation of a 980 nm laser, the two emission bands were detected in the UC emission spectrum, weak green band centered at 544 and 559 nm, and strong red band centered at 657 and 675 nm wavelengths in accordance with 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ion, respectively. The simple chemical formula equations, for explaining the site preference of Er3+ and Yb3+ ions in host crystal matrix, were generated by considering the Zn2TiO4 crystal structure, its crystal properties, and the effect of Er3+ and Yb3+ ions to the host crystal matrix. The UC emission intensity of the products was changed by varying ZnO/TiO2 mixing ratios, and Er3+ and Yb3+ concentrations. The best suitable condition for emitting the brightest UC emission was 1ZnO:1TiO2 doped with 3 mol% Er3+, 9 mol% Yb3+ fired at 1300 °C for 1 h.

Insight the Luminescence Properties of AlON: Eu, Mg Phosphor under VUV Excitation.

Owing to high quantum efficiency, adjustable composition and antioxidation properties of oxynitride phosphors, extensive investigations have focused on their photoluminescence properties under low-energy light excitation (UV or blue light). However, the vacuum ultraviolet (VUV) luminescence properties of oxynitride phosphors are rarely researched. Present work studies the structure and VUV luminescence properties of an oxynitride phosphor: AlON: Eu, Mg, which is synthesized by solid-state reaction. Under 147 nm excitation, it was found that AlON: Eu, Mg phosphor shows a blue emission band centered at about 470 nm. The first principle calculation is used to analyze the origin of the VUV absorption. Compared with BaMgAl10O17: Eu2+ phosphor, AlON: Eu, Mg phosphor shows better thermal stability.

Li3BaSrLa3(WO4)8:Eu3+ and Its Solid Solutions : A New Red Emitting Phosphor ‐ Structure, Synthesis and Appraisal of Optical Properties

AbstractSequences of red emitting Eu3+ activated Li3BaSrLa3(WO4)8 were, synthesized by following an accustomed solid state reaction method. The concentration of the Eu3+ ion was varied in the Li3BaSrLa3(WO4)8 host lattice in steps of 0.3. From the concentration optimization analysis, it was observed that the (Li3BaSrEu2.7La0.3(WO4)8) phosphor composition shows highest emission intensity. Further, we fixed the Eu3+ ion concentration, and efforts have been made to establish a solid solution amid the tungstate and molybdates. All the phosphor compositions exhibit broad absorption due to O → M (M=W/Mo), O → Eu charge transfer(CT) band and excellent photoluminescence properties, with intense electric dipole transition (7F0 → 5D2). The detailed optical studies were indicated in order to authorize that the Eu3+ ion resides at the non‐centrosymmetric site residence in the interior of the host lattice. The Judd – Ofelt spectral intensity parameters were calculated. The absolute quantum yield and lifetime of the red phosphors were also measured for selected compositions. It was observed that the selected phosphors yield a high value of QY (89.8 %) with enhanced absorption and emission properties. The best solid solution phosphor composition was used for LED fabrication by integrating with 395 nm near UV LED, forward biased at 20 mA. The leading optical characteristics of the phosphors may find versatile applications in the field of lighting (including SSL) as well as other essential fields.

Concentration and temperature dependent luminescence properties of Gd2MoO6:Eu3+ and white light generation from g-C3N4/Gd2MoO6:Eu3+ composite phosphor

The design and discovery of novel near-ultraviolet excitable phosphors has become a hot topic in academic research and practical applications, such as white light-emitting diodes for solid state lighting. The present work firstly reports the concentration/temperature dependent luminescence properties of the red emitting phosphor Gd2MoO6:Eu3+, synthesized by a typical solid state method. The as-prepared phosphor possesses a single monoclinic phase, as determined from XRD results. Upon excitation with near-ultraviolet light, the Gd2MoO6:Eu3+ phosphor exhibits a characteristic red emission corresponding to the 4f-4f transitions of the Eu3+ ions, in which the main electric dipole transition is 5D0→7F2. In addition, the concentration quenching mechanism and the activation energy for thermal quenching of the Eu3+ ions in Gd2MoO6 host was also investigated in detail. Furthermore, a series of novel near-ultraviolet excitable emitting-color tunable composite phosphors consisted of graphitic-phase nitrogen carbon (g-C3N4) and Gd2MoO6:Eu3+ is reported herein. It is interesting that white light emission is veritably generated by compositing two luminescence materials at an appropriate weight ratio of g-C3N4 to Gd2MoO6:Eu3+. The combination of an n-UV LED chip with the composite g-C3N4/Gd2MoO6:Eu3+ phosphor produces white light with a CRI value of ∼80.1 and a CCT value of 4244K. The obtained results indicate that the Gd2MoO6:Eu3+ and g-C3N4/Gd2MoO6:Eu3+ phosphors could be potential red and white emitting phosphors for application in white light-emitting diodes.

Effect of comburent ratios on combustion synthesis of Eu-doped β-SiAlON green phosphors

SiAlON phosphors doped with rare earths have attracted much attention on the application of light emitting diode (LEDs) benefitting from their outstanding thermal stability, chemical stability and broad emission band properties. In this work, Eu-doped β-SiAlON green phosphors with composition Si5.5Al0.5O0.5N7.5:0.035Eu2+ were prepared by a highly efficient combustion synthesis (CS) method. The effect of comburent ratios (i.e., Si & Al) were systematically investigated by adjusting the starting compositions of reactants. It was confirmed that the ratios of Si and Al reactants had an intense influence on the phase composition, microstructure and photoluminescence properties of as-synthesized phosphors by directly determining the systematic energy in CS. The as-prepared β-SiAlON:Eu2+ phosphors featured with high phase purity, uniform particle size of 3–5 μm, well-crystalline morphology and outstanding luminescent properties of green emission under UV or blue excitation were synthesized with 67.5 wt.% ratio of Si and no Al comburent.

Preparation and characterization of SiO2-coated Sr4A114O25:Eu2+, Dy3+/light conversion agent yellow phosphor

The SiO2-coated Sr4A114O25:Eu2+, Dy3+/light conversion agent yellow phosphor was prepared by the sol–gel method in alcohol/water system. The morphology, photochromic properties and water tolerance of the samples were analyzed and characterized by using XRD, SEM, FTIR, fluorescence spectrophotometer, spectroradiometer and pH meter. The results reveal that the silica and light conversion agent were successfully coated on the surface of Sr4A114O25:Eu2+, Dy3+. The emission peak shifted from 493 nm (Sr4A114O25:Eu2+, Dy3+) to 606 nm due to the cladding of the light conversion agent (LCA). But with the addition of silica, the property of light conversion agent was influenced by the hydrogen bonds and the electrostatic interactions between silica and light conversion agent. That caused the excitation energy of the light conversion agent risen, and the emission peak have a blue shift from 606 nm (Sr4A114O25:Eu2+, Dy3+/LCA) to 586 nm. Therefore, the composite phosphor was obtained that appeared yellow fluorescence while pink in the daylight. It is also important that the composite yellow phosphors have good water tolerance attributed to the coating of silica.

Application of composite phosphor ceramics by tape-casting in white light-emitting diodes

Abstract Composite phosphor ceramics were fabricated for white light-emitting diodes (LEDs) employing the tape-casting. Benefiting from the superposition of different emission spectrum, wider emission spectra of composite ceramics were reached, result in a higher color rendering index (CRI) of ceramic-based WLED. The composite structure and fluorescent property of composite ceramics were analyzed and the optical properties of ceramic-based WLED were tested. A ceramic-based WLED with a maximum CRI value of ∼83 was reached when (Ce,Gd):YAG and (Ce,Pr):YAG were employed for the composite ceramics.