Synthesis and characterization of Sr3Al2O6：Eu2＋, Dy3＋ phosphors prepared by sol-gel-combustion processing

A type of red luminescent Sr3Al2O6:Eu2+, Dy3+ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3- by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3Al2O6:Eu2+, Dy3+. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250 C. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of (Sr0.94Eu0.03Dy0.03)3Al2O6 phosphors sintered at 1250 ℃ lasts for over 1000 s when the excited source is cut off.     

Energy transfer in Y3Al5O12:Ce, Pr and CaMoO4:Sm, Eu phosphors

Non-radiative energy transfers (ET) from Ce³⁺ to Pr³⁺ in Y₃Al₅O₁₂:Ce³⁺, Pr³⁺ and from Sm³⁺ to Eu³⁺ in CaMoO₄:Sm³⁺, Eu³⁺ are studied based on photoluminescence spectroscopy and fluorescence decay patterns. The result indicates an electric dipole-dipole interaction that governs ET in the LED phosphors. For Ce³⁺ concentration of 0.01 in YAG:Ce³⁺, Pr³⁺, the rate constant and critical distance are evaluated to be 4.5×10⁻³⁶ cm⁶ s⁻¹ and 0.81 nm, respectively. An increase in the red emission line of Pr³⁺ relative to the yellow emission band of Ce³⁺, on increasing Ce³⁺ concentration is observed. This behavior is attributed to the increase of spectral overlap integrals between Ce³⁺ emission and Pr³⁺ excitation due to the fact that the yellow band shifts to the red spectral side with increasing Ce³⁺ concentration. In CaMoO₄:Sm³⁺, Eu³⁺, Sm³⁺-Eu³⁺ transfer occurs from ⁴G_5/2 of Sm³⁺ to ⁵D₀ of Eu³⁺. The rate constant of 8.5×10⁻⁴⁰ cm⁶ s⁻¹ and the critical transfer distance of 0.89 nm are evaluated.     

Luminescent characteristics of LiCaBo3:M (M=Eu, Sm, Tb, Ce, Dy) phosphor for white LED

LiCaBO₃:M (M=Eu³⁺, Sm³⁺, Tb³⁺, Ce³⁺, Dy³⁺) phosphors were synthesized by a normal solid-state reaction using CaCO₃, H₃BO₃, Li₂CO₃, Na₂CO₃, K₂CO₃, Eu₂O₃, Sm₂O₃, Tb₄O₇, CeO₂ and Dy₂O₃ as starting materials. The emission and excitation spectra were measured by a SHIMADZU RF-540 UV spectrophotometer. And the results show that these phosphors can be excited effectively by near-ultraviolet light-emitting diodes (UVLED), and emit red, green and blue light. Consequently, these phosphors are promising phosphors for white light-emitting diodes (LEDs). Under the condition of doping charge compensation Li⁺, Na⁺ and K⁺, the luminescence intensities of these phosphors were increased.     

Crystal structure and photoluminescence of (Y1−xCex)2Si3O3N4

Oxonitridosilicate phosphors with compositions of (Y_1−xCe_x)₂Si₃O₃N₄ (x=0−0.2) have been synthesized by solid state reaction method. The structures and photoluminescence properties have been investigated. Ce³⁺ ions have substituted for Y³⁺ ions in the lattice. The emission and excitation spectra of these phosphors show the characteristic photoluminescence spectra of Ce³⁺ ions. Based on the analyses of the diffuse reflection spectra and the PL spectra, a systematic energy diagram of Ce³⁺ ion in the forbidden band of sample with x=0.02 is given. The best doping Ce content in these phosphors is ∼2 mol%. The quenching temperature is ∼405 K for the 2 mol% Ce content sample. The luminescence decay properties were investigated. The primary studies indicate that these phosphors are potential candidates for application in three-phosphor-converted white LEDs.     

Synthesis and luminescence properties of Eu, Ce and Tb-activated Sr3La2(BO3)4 under UV excitation

The spectroscopic properties in UV-excitable range for the phosphors of Sr₃La₂(BO₃)₄:RE³⁺ (RE³⁺=Eu³⁺, Ce³⁺, Tb³⁺) were investigated. The phosphors were synthesized by conventional solid-state reactions. The photoluminescence (PL) spectra and commission international de I'Eclairage (CIE) coordinates of Sr₃La₂(BO₃)₄:RE³⁺ were investigated. The f-d transitions of Eu³⁺, Ce³⁺ and Tb³⁺ in the host lattices are assumed and corroborated. The PL and PL excitation (PLE) spectra indicate that the main emission wavelength of Sr₃La₂(BO₃)₄:Eu³⁺ is 611 nm, and Sr₃La₂(BO₃)₄:Ce³⁺ shows dominating emission peak at 425 nm, while Sr₃La₂(BO₃)₄:Tb³⁺ displays green emission at 487, 542, 582 and 620 nm. These phosphors were prepared by simple solid-state reaction at 1000 °C. There are lower reactive temperature and more convenient than commercial phosphors. The Sr₃La₂(BO₃)₄:Tb³⁺ applied to cold cathode fluorescent lamp was found to emit green light and have a major peak wavelength at around 542 nm. These phosphors may provide a new kind of luminescent materials under ultraviolet excitation.     

Synthesis and luminescent properties of nanoparticles GdCaAl3O7:RE (RE=Eu, Tb) via the sol-gel method

By using metal nitrates as starting materials and citric acid as complexing agent, GdCaAl₃O₇:Eu³⁺ and GdCaAl₃O₇:Tb³⁺ powder phosphors were prepared by a citrate-gel method. Thermal analysis (TG-DTG), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM), photoluminescence excitation and emission, as well as kinetic decays were employed to characterize the resulting samples. The results of the XRD indicated the precursor samples began to crystallize at 800 °C and the crystallinity increased with elevation the annealing temperature. TEM images showed that the phosphor particles were basically of spherical shape, with good dispersion about a particle size of around 40-70 nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617 nm corresponding to the forced electric dipole ⁵D₀-⁷F₂ transition of Eu³⁺, and at around 543 nm corresponding to the ⁵D₄-⁷F₅ transition of Tb³⁺. The dependence of photoluminescence intensity on Eu³⁺ (or Tb³⁺) concentration and annealing temperature were also studied in detail.     

Energy transfer and luminescent properties of Ce, Cr co-doped Y3Al5O12

The phosphors in the system Y_3−xAl_5-yO₁₂:xCe³⁺,yCr³⁺ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have absorption in the visible light region and give luminescence in the far-red region (∼688 nm), which are suitable for the application in the device of luminescent solar concentrator (LSC). In these phosphors, Ce³⁺ located at Y³⁺ site can effectively transfer its absorbed energy to Cr³⁺ at Al³⁺ site.     

Photoluminescence properties and synthesis of nano-sized YAG: Ce phosphor via novel synthesis method

This study reports an approach for enhancing the luminescent properties of Y₃Al₅O₁₂: Ce³⁺_0.07 using an organic compound precursor. The Y₃Al₅O₁₂: Ce³⁺_0.07 nano-sized phosphors had a relatively uniform particle size, approximately 50-80 nm, when sintered at 1200 °C for 1 h. The photoluminescence results showed the maximum peak intensity when the concentration of Ce³⁺ ions was 0.07 mol. The results suggest that nano-sized phosphors synthesized from organic compound precursors can be used as alternative efficiency emitting phosphors in the LED applications.     

Luminescence properties of cerium-doped di-strontium magnesium di-silicate phosphor by the solid-state reaction method

A series of Sr₂MgSi₂O₇:xCe³⁺ (x?=?1.0%, 2.0%, 3.0%, 4.0% and 5.0%) phosphors were synthesized by the solid-state reaction method. The phosphor with optimum thermoluminescence, photoluminescence and mechanoluminescence (ML) intensity was characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared techniques. The trapping parameters (i.e. activation energy, frequency factor and order of the kinetics) of each synthesized phosphor have been calculated using the peak shape method and the results have been discussed. Under ultraviolet excitation (325?nm), Sr₂MgSi₂O₇:xCe³⁺ phosphors were composed of a broad band peaking at 385?nm, belonging to the broad emission band which emits violet-blue color. Commission International de I’Eclairage coordinates have been calculated for each sample and their overall emission is near violet-blue light. In order to investigate the suitability of the samples for industrial uses, color purity and color rendering index were calculated. An ML intensity of optimum [Sr₂MgSi₂O₇:Ce³⁺ (3.0%)] phosphor increases linearly with increasing impact velocity of the moving piston which suggests that these phosphors can be used as fracto-ML-based devices. The time of the peak ML intensity and the decay rate did not change significantly with respect to increasing impact velocity of the moving piston.     

Effect of Eu,Tb codoping on the luminescent properties of Y2O3 nanorods

Red-emitting Y₂O₃:Eu³⁺ and green-emitting Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺, Tb³⁺ nanorods were synthesized by hydrothermal method. Their structure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The photoluminescence (PL) property of Y₂O₃:Eu³⁺,Tb³⁺ phosphor was investigated. In the same host (Y₂O₃), upon excitation with ultraviolet (UV) irradiation, it is shown that there are strong emissions at around 610 and 545 nm corresponding to the forced electric dipole ⁵D₀-⁷F₂ transition of Eu³⁺ and ⁵D₄-⁷F₅ transition of Tb³⁺, respectively. Different qualities of Eu³⁺and Tb³⁺ ions are induced into the Y₂O₃ lattice. From the excitation spectrum, we speculate that there exists energy transfer from Tb³⁺ to Eu³⁺ ions .The emission color of powders reveals regular change in the separation of light emission. These powders can meet with the request of optical display material for different colors or can be potentially used as labels for biological molecules.     

H_3BO_3对Y_(1.98)O_3:Eu_(0.01),Dy_(0.01)红色长余辉发光材料结构和余辉性能的影响

采用高温固相法制备了发光样品Y1.98O3:Eu3+0.01,Dy3+0.01.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、荧光光谱仪、单光子计数器测试了不同含量的H3BO3对Y1.98O3:Eu3+0.01,Dy3+0.01物相结构、颗粒形貌、发光性能、余辉性能的影响.结果表明当H3BO3含量低于8%(mol)时,样品可保持Y2O3晶格结构,且样品颗粒随H3BO3的含量增加逐渐增大.样品光致发光由Eu3+离子电子的5D0→7FJ跃迁所致,主峰位于612 nm,且发光强度随H3BO3含量的增加呈线性增强.随着H3BO3含量的增加,样品余辉衰减时间逐渐增加,热释光谱分析表明H3BO3的加入增加了基质陷阱能级的深度与浓度,故而导致样品长余辉性能的变化.     

The structure and luminescence properties of a novel orange emitting phosphor Y3MnxAl5−2xSixO12

A series of phosphors with the composition Y₃Mn_xAl_5−2xSi_xO₁₂ (x=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6) was prepared through solid state reactions. X-ray powder diffraction analysis of samples shows that when co-doping content does not exceed 16% of Al³⁺, equimolar co-doping of Mn²⁺ and Si⁴⁺ does not change the garnet structure of phosphors, but makes the interplanar distance to decrease a certain extent. However, if the co-doping content exceeds 16%, new phases will form in the samples. The excitation and emission spectra of samples show that Mn²⁺ in Y₃Mn_xAl_5−2xSi_xO₁₂ emits broadband orange light (peak wavelength varies from 586 to 593 nm). With an increment in co-doping content, the emission intensity of the phosphors increases when the value of x is lower than 0.1 while it decreases when it is higher than 0.1 and the emission peak moves to a longer wavelength.     

Low thermal quenching and high-efficiency Ce, Tb-co-doped Ca3Sc2Si3O12 green phosphor for white light-emitting diodes

Low thermal quenching and high-efficiency Ca₃Sc₂Si₃O₁₂:Ce³⁺ (CSSO:Ce³⁺) phosphors with co-doping Tb³⁺ ion were prepared by a solid state method and the properties of these phosphors were investigated. The results showed that co-doping of Tb³⁺ not only enhances the photoluminescence remarkably and decreases the thermal quenching of the phosphor, but also heightens the performances of the LEDs fabricated with the phosphor. A high-efficiency and low color temperature white LED was fabricated with the prepared CSSO:1%Ce³⁺, 0.5%Tb³⁺ and a red phosphor, indicating that CSSO:1%Ce³⁺,0.5%Tb³⁺ phosphor is a suitable green phosphor for the fabrication of high-efficiency white LEDs.     

Effect of boric acid on structure,morphology and luminescent properties of divalent europium doped calcium aluminate phosphors

Blue phosphors Ca_1 − xAl₂O₄: xEu²⁺ were prepared by high temperature solid-state method. Their structure, morphology and luminescent properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and fluorescence spectroscopy. The effect of different amounts of fluxing agent H₃BO₃ on structure, morphology and luminescent properties of blue phosphors Ca_1 − xAl₂O₄: xEu²⁺ luminous intensity caused by different amount of H₃BO₃ was also investigated. The amount of H₃BO₃ doped Ca_1 − xAl₂O₄: xEu²⁺ in optimal luminous intensity had been determined. The results showed that both the excitation and emission spectra of samples were all broad bands, and that the peak of emission spectra was near 442 nm, which was corresponding to the 4f⁶5d → 4f⁷ transition of Eu²⁺ illuminating blue light. Ca_1 − xAl₂O₄: xEu²⁺ (x = 3.5 mol%) could be gained with good morphology and the best luminous intensity when H₃BO₃ mass ratio was 0.5 wt%.     

Dy含量对红色长余辉发光材料Sr3Al2Ｏ6:Eu2＋,Dy3＋性能的影响

采用溶胶凝胶法制备了Sr₃Al₂Ｏ₆:Eu^2＋,Dy^3＋红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr₃Al₂Ｏ₆,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr₃Al₂Ｏ关键词： 红色长余辉 3Al₂Ｏ₆')" href="#">Sr₃Al₂Ｏ₆ 溶胶凝胶法     

Luminescence in trivalent rare earth activated Sr4Al2O7 phosphor

In this paper we report the combustion synthesis of trivalent rare-earth (RE³⁺ = Dy, Eu and Ce) activated Sr₄Al₂O₇ phosphor. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) and photoluminescence (PL) techniques. Photoluminescence emission peaks of Sr₄Al₂O₇:Dy³⁺ phosphor at 474 nm and 578 nm in the blue and yellow region of the spectrum. The prepared Eu³⁺ doped phosphors were excited by 395 nm then we found that the characteristics emission of europium ions at 615 nm (⁵D₀?⁷F₂) and 592 nm (⁵D₀?⁷F₁). Photoluminescence (PL) peaks situated at wavelengths of 363 and 378 nm in the UV region under excitation at around 326 nm in the Sr₄Al₂O₇:Ce³⁺ phosphor.     

Synthesis and luminescent properties of nanoparticles LaSrAl3O7:Eu, Tb

Phosphors of nanoparticles LaSrAl₃O₇:RE³⁺(REEu, Tb) have been prepared by a sol–gel method. The structure and luminescent properties of LaSrAl₃O₇:Eu³⁺ and LaSrAl₃O₇:Tb³⁺ phosphors were characterized by X-ray diffraction and atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized. From X-ray diffraction (XRD) patterns, it is indicated that the phosphor LaSrAl₃O₇ forms without impurity phase at 900 °C. From atomic force microscopy (AFM) images, it is shown that the crystal size of the phosphores are about 60–80 nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617 nm corresponding to the forced electric dipole ⁵D₀–⁷F₂ transition of Eu³⁺, and at around 545 nm corresponding to the ⁵D₄–⁷F₅ transition of Tb³⁺. The dependence of photoluminescence intensity on Eu³⁺(or Tb³⁺) concentration and annealing temperature were also studied in detail.     

The structure and luminescence properties of long afterglow phosphor Y3−xMnxAl5−xSixO12

A series of phosphors with the composition Y_3−xMn_xAl_5−xSi_xO₁₂ (x=0, 0.025, 0.050, 0.075, 0.150, 0.225, 0.300) were prepared with solid state reactions. The X-ray powder diffraction analysis of samples shows that the substitution of Mn²⁺ and Si⁴⁺ does not change the garnet structure of phosphors, but makes the interplanar distance decrease to a certain extent. The emission spectra show that Mn²⁺ in Y₃Al₅O₁₂ emits yellow-orange light in a broad band. With the increment of substitution content, the emission intensity of the phosphors increases firstly then decreases subsequently, and the emission peak moves to longer wavelength. Afterglow spectra and decay curves show that all the Mn²⁺ and Si⁴⁺ co-doped samples emit yellow-orange light with long afterglow after the irradiation of ultraviolet light. The longest afterglow time is 18 min. Thermoluminescence measurement shows that there exist two kinds of traps with different depth of energy level and their depth decreases with the increment of substitution content.     

Y2O3: Eu,Dy的制备与红色长余辉发光性能研究

采用高温固相法合成发光样品Y₂O₃：Eu³⁺_0.01和Y₂O₃：Eu³⁺_0.01,Dy³⁺_0.01.X射线衍射分析(XRD)表明样品保持Y₂O₃晶格结构,掺入的Eu³⁺和Dy³⁺对Y_{2关键词： 长余辉 2}O₃')" href="#">Y₂O₃ 稀土掺杂 陷阱     

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

A flux fusion method was used to obtain the various sizes of Eu³⁺-activated Y₂O₃ 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 Eu³⁺-activated Y₂O₃. In particular, when a BaF₂ flux was used during the reaction at 1450 °C for 3 h, the photoluminescence (PL) intensity of Eu³⁺-activated Y₂O₃ 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 Eu³⁺-activated Y₂O₃ phosphor were predominantly dependent upon the type and concentration of flux material and synthetic temperature.