Flux Fusion Method Research Articles

Synthesis and Luminescence Properties of La2O2S:RE3+ (RE3+ = Ce3+, Dy3+, Eu3+ and Tb3+) Submicron Size Phosphors for Lamp Industry

RE3+(RE3+ = Ce3+, Dy3+, Eu3+ and Tb3+) doped La2O2S phosphors was synthesized by solid state flux fusion method and their down conversion spectral properties were studied as a function different RE3+ concentrations and reported in this paper. The solid state flux fusion results in well crystallized hexagonal shaped phosphor particles. The samples were characterized by XRD, SEM, FT-IR photoluminescence (PL) and CIE colour co-ordinates techniques. The lanthanum oxysulphide (La2O2S) phosphor doped with Ce3+ shows broad band emission with peak at 390 nm and 415 nm when excited at 340 nm excitation. La2O2S:Dy3+ shows efficient blue and yellow band emissions at 480 nm and 572 nm. La2O2S:Eu3+ phosphor shows an orange and red emission at 590 nm and 615 nm. Whereas La2O2S:Tb3+ phosphor shows weak blue emission at 488 nm and strong green 545 nm. The excitation spectra used for the La2O2S:RE3+ (where RE3+ = Ce3+, Dy3+, Eu3+ and Tb3+) phosphors is in the near UV region extending from 350 to 400 nm, which is characteristics of near UV excited LED. The effect of the RE3+ (RE3+= Ce3+, Dy3+, Eu3+ and Tb3+) concentration on the luminescence properties of La2O2S:RE3+ phosphors were also studied. The investigated prepared La2O2S phosphors may be suitable for a near UV excited W-LED. Keywords: Oxysulphide, SEM, FT-IR, PL, SSL, CIE.

Symmetry fractionalization and anomaly detection in three-dimensional topological phases

In a phase with fractional excitations, topological properties are enriched in the presence of global symmetry. In particular, fractional excitations can transform under symmetry in a fractionalized manner, resulting in different Symmetry Enriched Topological (SET) phases. While a good deal is now understood in $2D$ regarding what symmetry fractionalization patterns are possible, the situation in $3D$ is much more open. A new feature in $3D$ is the existence of loop excitations, so to study $3D$ SET phases, first we need to understand how to properly describe the fractionalized action of symmetry on loops. Using a dimensional reduction procedure, we show that these loop excitations exist as the boundary between two $2D$ SET phases, and the symmetry action is characterized by the corresponding difference in SET orders. Moreover, similar to the $2D$ case, we find that some seemingly possible symmetry fractionalization patterns are actually anomalous and cannot be realized strictly in $3D$. We detect such anomalies using the flux fusion method we introduced previously in $2D$. To illustrate these ideas, we use the $3D$ $Z_2$ gauge theory with $Z_2$ global symmetry as an example, and enumerate and describe the corresponding SET phases. In particular, we find four non-anomalous SET phases and one anomalous SET phase, which we show can be realized as the surface of a $4D$ system with symmetry protected topological order.

1.06 μm laser absorption properties of Sm2O2S prepared by flux method

Laser stealth absorption material Sm2O2S was successfully synthesized by a solid state flux fusion method. The phase composition, morphology and optical property were investigated by X-ray diffraction with Rietveld structure refinement, scanning electron microscopy, thermogravimetry–differential scanning calorimetry and ultraviolet–visible spectrophotometer. The results showed that Li2CO3/Na2CO3 composites were the optimal flux for the crystal formation. Na2CO3 plays an important role during the reaction. With the increase of temperature, crystal structure became regular. The hexagonal shape powders could be achieved above 1100 °C. Furthermore, the as-prepared Sm2O2S powder had an intense absorption around 1.06 μm, causing by electron transitions from ground state 6H5/2 to excited state 6F9/2. The study indicated that Sm2O2S can be a promising 1.06 μm laser absorption material.

UVB-emitting Gd(3+)-activated M2O2S (where M = La, Y) for phototherapy lamp phosphors.

Gd(3+)-activated oxysulphide (M2O2S) may be used to study Photoluminescence (PL) properties with respect to phototherapy. Gd(3+)-activated phosphor materials are widely used for phototherapy lamps. The Gd(3+) ion gives characteristic Narrow-Band (NB) emissions, in particular in the ultraviolet (UV) light region, that are used to treat more than 50 types of skin diseases. In this paper, M2O2S oxysulphide doped with Gd(3+) was synthesized by the solid-state flux fusion method and its down conversion spectral properties were studied as a function of different Gd(3+) concentrations. The sample was characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and PL and the crystal structure was also studied. The lanthanum oxysulphide (La2O2S)-activated Gd(3+) ion showed a sharp emission peak at 314 nm when excited at 275 nm excitation, whereas the yttrium oxysulphide (Y2O2S)-activated Gd(3+) ion showed a sharp emission at 316 nm when excited by 272 nm. The effect of concentration of the Gd(3+) ion on the luminescence properties of M2O2S:Gd(3+) phosphor was also studied. These phosphor materials activated with the Gd(3+) ion may be suitable for phototherapy lamps, which are used to treat many types of skin diseases such as psoriasis, vitiligo, or scleroderma.

Rare Earth Based Upconverting Materials for Solar Cell Application

ABSTRACTBasic spectroscopic studies of Yb and Er-doped M2O2S (M= Gd, La,Y) phosphor was reported with particular attention to its upconversion properties under 1550 nm excitation. Since the absorption spectra of Co2+overlaps with Er3+(4I13/2→4I15/2) at near infrared (NIR) region, we are proposing the concept of an efficiency enhancement of infrared upconverting phosphors as an energy converting material that could potentially improve the efficiency of Si solar cells in bifacial configuration. Different concentrations of Er3+/Co2+ phosphors were synthesized by solid state flux fusion method. The phosphor powders were well crystallized in a hexagonal shape with an average size 4 mm. Preliminary upconversion analysis of singly Er3+ and doubly Co2+/Er3+ doped Y2O2S under 980 and 1550 nm excitation indicates that the composition has to be optimized to understand the role of Co2+ in the system.

Synthesis and spectroscopy of color tunable Y 2O 2S:Yb 3+,Er 3+ phosphors with intense emission

Trivalent ytterbium and erbium doped in yttrium oxysulfide (Y 2O 2S:Yb 3+,Er 3+) phosphors were synthesized by solid state flux fusion method and their upconversion spectral properties were studied as a function of different Yb 3+ concentrations. The solid state flux fusion results in well crystallized hexagonal shaped phosphor particles with an average size of 3.8 μm. The detailed optical characterizations such as absorption, emission, and fluorescence decay were performed to explore the emission processes in the UV–VIS–NIR as well as to quantitatively estimate the fluorescence quantum yield. Upconversion spectral studies show that for all the compositions, green emissions are stronger; in particular the green emission intensity is 1.7 times stronger than the red intensity with composition of 9 mol% Yb 3+ and 1 mol% Er 3+. Mechanisms of upconversion by two-photon and energy transfer processes are interpreted and explained. The color coordinates are measured and the color tunability was analyzed as a function of the 980 nm excitation power. Results show that the Y 2O 2S:Yb 3+,Er 3+ phosphor offers power dependent color tuning properties where the emission color can be tuned from 490 to 550 nm by simply changing the 980 nm excitation power from 10 to 50 mW.

The effect of flux materials on the physical and optical properties of Eu 3+-activated yttrium oxide phosphors

A flux fusion method was used to obtain the various sizes of Eu 3+-activated Y 2O 3 red phosphors. The flux material was selected as an independent variable to control the physical properties of phosphor particles and their effects on the morphology and size distribution of phosphors were examined by scanning electron microscopy. The concentration of the flux materials and synthetic temperature were optimized for maximal photoluminescence intensity. Fluoride-based flux materials were found to work for the crystal formation of Eu 3+-activated Y 2O 3. In particular, when a BaF 2 flux was used during the reaction at 1450 °C for 3 h, the photoluminescence (PL) intensity of Eu 3+-activated Y 2O 3 was 25% higher than that without a flux and spherical phosphors had a mean particle size of 4–5 μm. The morphology and size distribution of the synthesized Eu 3+-activated Y 2O 3 phosphor were predominantly dependent upon the type and concentration of flux material and synthetic temperature.

Effect of Mg 2+ and Ti IV doping on the luminescence of Y 2O 2S:Eu 3+

The Y 2O 2S:Eu 3+,Mg 2+,Ti IV ( x Eu = 0.028, x Mg = 0.086, x Ti = 0.03) materials were prepared with the flux fusion method. According to X-ray powder diffraction, the materials had the hexagonal crystal structure. The emission of Y 2O 2S:Eu 3+,Mg 2+,Ti IV was centered at 627 nm ( λ exc : 250 nm) due to the 5D 0 → 7F 2 transition of Eu 3+. The excitation spectra ( λ em : 627 nm) showed broad bands at 240 and 320 nm due to the O 2− → Eu 3+ and S 2− → Eu 3+ charge transfer transitions, respectively. The latter band can also overlap with the Ti → Eu 3+ energy transfer. In the excitation spectra with synchrotron radiation, in addition to the O 2− → Eu 3+ and S 2− → Eu 3+ charge transfer transitions, excitation over the band gap was observed at 4.8 eV (258 nm). The red persistent luminescence due to the 5D 0 → 7F 2 emission from Eu 3+ residing in the regular Y 3+ site of the host was ca. 10 min with 1 min fluorescent lamp irradiation. In addition, a very broad band was observed at 600 nm probably due to the Ti 3+ emission.

Effects of Host Doping on Spectral and Long-Lasting Properties of Sm 3+-Doped Y 2O 2S

Gd- or Lu-doped long afterglow red phosphor Y 2O 2S:Sm 3+ was synthesized using the high temperature flux fusion method. The obtained phosphors were analyzed using X-ray diffraction to determine the crystal structure, and the phase analyses show that the product is in single phase. The luminescence spectra and decay curve were measured on a Hitachi F-4500 fluorescence spectrophotometer. The decay time was determined on an ST-900PM weak light photometer. The analyses show that host doping of Lu improves both luminescence and decay time of the materials. The concentration of doped Lu and Sm was varied in order to determine the optimal condition and to synthesize the product with the best properties. The mechanism of the long afterglow was also briefly discussed.

Spectra and long-lasting properties of Sm3+-doped yttrium oxysulfide phosphor

We reported, for the first time to the best of our knowledge, the Sm3+-doped yttrium oxysulfide phosphors has reddish orange long-lasting phosphorescence. The phosphor show prominent luminescence in reddish orange due to the electronic transitions of 4G5/2→6HJ (J = 5/2, 7/2, 9/2), the afterglow color of this type of phosphors is a mixture of the three above mentioned electronic transition emissions and have a little different when the concentration of the Sm3+ dopant changes. Synthesis procedure of the Sm3+-yttrium oxysulfide reddish orange phosphor through the flux fusion method with binary flux compositions was presented. The synthesized phosphors were analyzed using X-ray diffraction (XRD) to interpret the structural characterization. The XRD analysis result reveal that the Y2O2S:Sm3+ phosphor synthesized with a binary flux composition containing (S and Na2CO3 at a ratio of 1:1 at 30wt.% of total raw material) at 1050°C for 3h was in single-phase. Luminescence properties of the Y2O2S:Sm3+ long-lasting phosphor was analyzed by measuring the excitation spectra, emission spectra and afterglow decay curve. The mechanism of the strong afterglow from Y2O2S:Sm3+ was also discussed in this paper.

Low-Voltage Cathodoluminescence Properties of the Y 2 O 2 S : Eu Red Light Emitting Phosphor Screen in Field-Emission Environments

phosphors doped with different concentrations of Eu were fabricated by a high-temperature flux fusion method. For applications in field emission displays, phosphor powders were electrophoretically deposited on an indium-tin oxide coated glass substrate to form a phosphor screen. Cathodoluminescence properties of phosphor screens were examined at a low excitation voltage of 5 kV in a high-vacuum chamber and characteristics of phosphors, including brightness and wavelength data, are presented and discussed. The red emission brightness for the phosphor screens can be significantly improved by adjustment of the Eu additions, which decrease the coordinate slightly, while having no significant influence on the color performance. Considering the effects of Eu concentrations on red light emission spectra and brightness for phosphor screens, it is found that brightness for phosphor screens could be obtained up to with chromaticity of and and the Eu dopant concentration is suggested to be in the range 6-7.5 wt %. © 2002 The Electrochemical Society. All rights reserved.

Synthesis of Eu3+-activated yttrium oxysulfide red phosphor by flux fusion method

Abstract Synthesis of the yttrium oxysulfide red phosphor by the flux fusion method was presented. Effects of flux compositions and sintering conditions on the shape and size distribution of phosphor were studied. In addition, the optimization of firing conditions was also conducted. After firing phosphor with a flux containing (S+Na2CO3+Li3PO4+K2CO3)/(S+Li2CO3+K2CO3) at a ratio of 3:1 at 1150°C for 2.5 h, Y2O2S:Eu3+ phosphor was obtained without any Y2O3 as a second phase. The nearly spherical phosphor powder exhibited a mean particle size of 3 μm and a rather sharp particle size distribution. Y2O2S:Eu3+ red phosphor illuminated the most red color light with an applied probe current density of 0.51 μA/cm2.

Luminescent mechanisms of ZnS:Cu:Cl and ZnS:Cu:Al phosphors

ZnS:Cu:Cl and ZnS:Cu:Al phosphors are fabricated by a flux fusion method to be used in cathode ray tube (CRT) monitors for green emission. The emission spectra of the phosphors depend on the Cu concentration. A series of luminescence measurements have been conducted, and several models are applied to explain the luminescent phenomenon of these phosphors. It is revealed that ZnS:Cu:Cl and the ZnS:Cu:Al phosphors exhibit green emission yet their luminescence mechanisms are different. The emission spectrum from the as-fabricated green phosphors is not a typical Gaussian distribution. The combination of blue and green band luminescence is attributed to the green-luminescence quenching derived from the interstitial Cu + ions.

Spectral properties of Eu3+-activated yttrium oxysulfide red phosphor

The effects of Eu on the spectral properties of Y2O2S have been investigated. The Y2O2S:Eu phosphor powders were prepared with a flux fusion method and electrophoretically deposited on an ITO-coated glass substrate to form a thin layer. Both cathodoluminescence and photoluminescence emission spectra of Y2O2S:Eu were measured. The highly intense emission lines at 616 and 626 nm are attributed to the transition from 5D0 to 7F2 levels. The color of Y2O2S:Eu phosphor varies from orange to red as the Eu concentration increases from Eu/Y=0.025 (molar ratio) to 0.06. The luminescence decay times are shorter than 1.1 ms for Eu concentrations ranging from 0.025 to 0.06 (Eu/Y molar ratio). The luminescent color becomes redder but less bright as the Eu concentration is increased.

ほう酸系フラックス溶融法による高純度酸化鉄の製造 Ｉ 亜鉛浸出残さ脱鉄処理で得られる酸化鉄の高純度化

ほう酸系フラックス溶融法による高純度酸化鉄の製造 Ｉ 亜鉛浸出残さ脱鉄処理で得られる酸化鉄の高純度化

Expeditious method of dissolving Amber and Copal

Synthesis of the yttrium oxysulfide red phosphor by the flux fusion method was presented. Effects of flux compositions and sintering conditions on the shape and size distribution of phosphor were studied. In addition, the optimization of firing conditions was also conducted. After firing phosphor with a flux containing (S+Na2CO3+Li3PO4+K2CO3)/(S+Li2CO3+K2CO3) at a ratio of 3:1 at 1150°C for 2.5 h, Y2O2S:Eu3+ phosphor was obtained without any Y2O3 as a second phase. The nearly spherical phosphor powder exhibited a mean particle size of 3 μm and a rather sharp particle size distribution. Y2O2S:Eu3+ red phosphor illuminated the most red color light with an applied probe current density of 0.51 μA/cm2.