Combustion synthesis of Sr3MgSi2O8:Eu and Sr2MgSi2O7:Eu phosphors

Sr₃MgSi₂O₈:Eu²⁺ and Sr₂MgSi₂O₇:Eu²⁺ phosphors find uses in applications such as plasma display panel (PDP), solid-state lighting, longafter glow. Preparation of these phosphors by a modified combustion synthesis is described in this paper. As-prepared samples did not show photoluminescence. After reducing the samples at 900 °C, characteristic Eu²⁺ emission was observed. Preparation of these phosphors by using similar methods helped clarifying various results obtained for Sr₃MgSi₂O₈:Eu²⁺ by different investigators.     

Enhanced luminescent properties of long-persistent Sr2MgSi2O7:Eu, Dy phosphor prepared by the co-precipitation method

Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors were prepared by the (aminopropyl)-triethoxysilane (APTES) co-precipitation method. Effects of synthesis temperature on the crystal characteristics, luminescent properties and afterglow performance of Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors have been discussed in detail and compared with the corresponding commercial product. The experimental results indicated that the sample could be synthesized at a relatively lower temperature and had better performance on the above-mentioned properties using the co-precipitation method.     

Effects of dopant concentrations on phosphorescence properties of Eu/Dy-doped Sr3MgSi2O8

Long afterglow Sr₃MgSi₂O₈: Eu, Dy phosphor with high brightness was prepared by sintering at high temperature and weak reductive atmosphere. The luminescent properties of this photoluminescent pigment were studied systematically by investigating concentration effects. The analytical results indicated that the main emission peaks appear at 482 nm. The excitation and emission spectra of this phosphor show that both of them are broadband. This is ascribed to the 4f⁷→4f⁶5d¹ transition of Eu²⁺ in the pigment matrix, which is in good agreement with the calculated value of 470 nm, and implies that luminescent centers Eu²⁺ occupy the deca-coordinated Sr²⁺ sites with the host of Sr₃MgSi₂O₈.     

Emission analysis of Eu:MgLaLiSi2O7 powder phosphor

Newly synthesized reference MgLaLiSi₂O₇ and red luminescent Eu³⁺:MgLaLiSi₂O₇ powder phosphors have been successfully developed by a solid-state reaction method to analyze their emission and structural properties from the measurement of their XRD, SEM, FTIR and PL spectra. Emission spectra of Eu³⁺ powder phosphors have shown strong red emissions at 613 nm (⁵D₀→⁷F₂). These phosphors have also shown bright red emissions under a UV source. Based on the red emission performance, the Eu³⁺ concentration has been optimized to be at 0.3 mol%.     

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.     

Sr2CeO4:Eu and Sr2CeO4:5 mol% Eu, 3 mol% Dy microphosphors: Wet chemistry synthesis from hybrid precursor and photoluminescence properties

In this article, Sr₂CeO₄:x mol% Eu³⁺ and Sr₂CeO₄:5 mol%Eu³⁺, 3 mol% Dy³⁺ phosphors were synthesized from assembling hybrid precursors by wet chemical method. As-prepared samples present uniform grain-like morphology and the particle size is about 0.2 μm. The luminescence spectra of Sr₂CeO₄:x mol% Eu³⁺ have been measured to examine the influence of the intensity of red emission lines for Eu³⁺ on the concentration of Eu³⁺, showing that the intensity of the red emission increases with an increase of the concentration from 1 to 5 mol%. Additionally, from the emission spectra of Sr₂CeO₄:5 mol%Eu³⁺, 3 mol% Dy³⁺ phosphors, the characteristic lines of Dy³⁺ have also been observed. This result indicates that there also exists an energy transfer process between Sr₂CeO₄ and Dy³⁺.     

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.     

A potential red-emitting phosphor CaSrAl2SiO7:Eu for near-ultraviolet light-emitting diodes

A novel red-emitting phosphor CaSrAl₂SiO₇:Eu³⁺ was firstly synthesized through the high temperature solid state reaction at 1300 °C. The structure, diffuse reflection spectra, photoluminescence spectra, color-coordinate parameters and quantum efficiencies (QE) of phosphors were investigated. The obtained CaSrAl₂SiO₇:Eu³⁺ phosphors have the same structure with that of the Ca₂Al₂SiO₇ and Sr₂Al₂SiO₇ phosphor, which have the melilite structure. Optical properties were studied as a function of Eu³⁺ concentration x, when x>0.14, the intensity of absorption of the f–f transitions of Eu³⁺ at 393 nm is stronger than that of the broad charge transfer transition band (CTB) around 254 nm, and which matches well with the output lights of NUV–LEDs, whereas, the concentration of Eu³⁺x≤0.14, the absorption of 393 nm is weaker than that of CTB. The underlying reason of Eu³⁺ concentration on their luminescent properties was investigated and discussed in detail. As a result, comparing with the commercial red phosphor Y₂O₂S:Eu³⁺, the CaSrAl₂SiO₇:xEu³⁺ (x>0.14) phosphor exhibited excellent color purity and much higher brightness and could be considered as promising red phosphors for NUV–LEDs.     

Photoluminescence properties of Sr1-xSi2O2N2: Eux as green to yellow-emitting phosphor for blue pumped white LEDs

This study evaluated potential applications of green to yellow-emitting phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) in blue pumped white light emitting diodes. Sr_1-xSi₂O₂N₂: Eu²⁺_x was synthesized at different Eu²⁺ doping concentrations at 1450 °C for 5 h under a reducing nitrogen atmosphere containing 5% H₂ using a conventional solid reaction method. The X-ray diffraction patterns of the prepared phosphor (Sr_1-xSi₂O₂N₂: Eu²⁺_x) were indexed to the SrSi₂O₂N₂ phase and an unknown intermediate phase. The photoluminescence properties of these phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) showed that the samples were excited from the UV to visible region due to the strong crystal field splitting of the Eu²⁺ ion. The emission spectra under excitation of 450 nm showed a bright color at 545-561 nm. The emission intensity increased gradually with increasing Eu²⁺ doping concentration ratio from 0.05 to 0.15. However, the emission intensity decreased suddenly when the Eu²⁺ concentration ratio was >0.2. As the doping concentration of Eu²⁺ was increased, there was a red shift in the continuous emission peak. These results suggest that Sr_1-xSi₂O₂N₂: Eu₂⁺_x phosphor can be used in blue-pumped white light emitting diodes.     

Photoluminescence and afterglow behavior of Eu, Dy and Eu, Dy in Sr3Al2O6 matrix

This paper reports the photoluminescence and afterglow behavior of Eu²⁺ and Eu³⁺ in Sr₃Al₂O₆ matrix co-doped with Dy³⁺. The samples containing Eu²⁺ and Eu³⁺ were prepared via solid-state reaction. X-ray diffraction (XRD), photo luminescent spectroscope (PLS) and thermal luminescent spectroscope (TLS) were employed to characterize the phosphors. The comparison between the emission spectra revealed that Sr₃Al₂O₆ phosphors doped with Eu²⁺, Dy³⁺ and Eu³⁺, Dy³⁺ showed different photoluminescence. The phosphor doped with Eu³⁺, Dy³⁺ showed an intrinsic f-f transition generated from Eu³⁺, with two significant emissions at 591 and 610 nm. However, the phosphor doped with Eu²⁺, Dy³⁺ revealed a broad d-f emission centering around 512 nm. After the UV source was turned off, Eu²⁺, Dy³⁺ activated Sr₃Al₂O₆ phosphor showed excellent afterglow while Eu³⁺, Dy³⁺ activated phosphor almost showed no afterglow. Thermal simulated luminescence study indicated that the persistent afterglow of Sr₃Al₂O₆: Eu²⁺, Dy³⁺ phosphor was generated by suitable electron traps formed by the co-doped rare-earth ions (Dy³⁺) within the host.     

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     

白光LED用LiBaBO3:Eu2+材料发光特性研究

采用高温固相法制备了LiBaBO₃:Eu²⁺绿色发光材料.测量了Eu²⁺浓度为1mol%时样品的激发与发射光谱,其发射光谱为双峰宽谱,主峰分别为482和507nm,与理论计算值符合很好;监测482nm发射峰时,对应激发光谱的峰值为287和365nm,监测507nm发射峰时,对应的激发峰为365和405nm.研究了Eu²⁺浓度对材料发射光谱的影响,结果显示,随Eu²⁺浓度的增大,蓝、绿发射峰均发生了     

A white light emitting phosphor Sr1.5Ca0.5SiO4:Eu, Tb, Eu for LED-based near-UV chip: Preparation, characterization and luminescent mechanism

In this work, we report preparation, characterization and luminescent mechanism of a phosphor Sr_1.5Ca_0.5SiO₄:Eu³⁺,Tb³⁺,Eu²⁺ (SCS:ETE) for white-light emitting diode (W-LED)-based near-UV chip. Co-doped rare earth cations Eu³⁺, Tb³⁺ and Eu²⁺ as aggregated luminescent centers within the orthosilicate host in a controlled manner resulted in the white-light phosphors with tunable emission properties. Under the excitation of near-UV light (394 nm), the emission spectra of these phosphors exhibited three emission bands: one broad band in the blue area, a second band with sharp lines peaked in green (about 548 nm) and the third band in the orange-red region (588-720 nm). These bands originated from Eu²⁺ 5d→4f, Tb³⁺⁵D₄→⁷F_J and Eu³⁺⁵D₀→⁷F_J transitions, respectively, with comparable intensities, which in return resulted in white light emission. With anincrease of Tb³⁺ content, both broad Eu²⁺ emission and sharp Eu³⁺ emission increase. The former may be understood by the reduction mechanism due to the charge transfer process from Eu³⁺ to Tb³⁺, whereas the latter is attributed to the energy transfer process from Eu²⁺ to Tb³⁺. Tunable white-light emission resulted from the system of SCS:ETE as a result of the competition between these two processes when the Tb³⁺ concentration varies. It was found that the nominal composition Sr_1.5Ca_0.5SiO₄:1.0%Eu³⁺, 0.07%Tb³⁺ is the optimal composition for single-phased white-light phosphor. The CIE chromaticity calculation demonstrated its potential as white LED-based near-UV chip.     

Synthesis and luminous characteristics of Ba2MgSi2−xAlxO7: 0.1Eu, 0.1Mn phosphor for WLED

The shift of the emission band to longer wavelength (yellow-orange) of the Ba₂MgSi_2−xAl_xO₇: 0.1Eu²⁺ phosphor under the 350-450 nm excitation range has been achieved by adding the codoping element (Mn²⁺) in the host. The single-host silicate phosphor for WLED, Ba₂MgSi_2−xAl_xO₇: 0.1Eu²⁺, 0.1Mn²⁺ was prepared by high-temperature solid-state reaction. It was found experimentally that, its three-color emission peaks are situated at 623, 501 and 438 nm, respectively, under excitation of 350-450 nm irradiation. The emission peaks at 438 and 501 nm originate from the transition 5d to 4f of Eu²⁺ ions that occupy the two Ba²⁺ sites in the crystal of Ba₂MgSi_2−x Al_xO₇, while the 623 nm emission is attributed to the energy transfer from Eu²⁺ ions to Mn²⁺ ions. The white light can be obtained by mixing the three emission colors of blue (438 nm), green (501 nm) and red (623 nm) in the single host. When the concentrations of the Al³⁺, Eu²⁺ and Mn²⁺ ions were 0.4, 0.1 and 0.1 mol, respectively, the sample presented intense white emission. The addition of Al ion to the host leads to a substantial change of intensity ratio between blue and green emissions. White light could be obtained by combining this phosphor with 405 nm light-emitting diodes. The near-ultraviolet GaN-based Ba₂MgSi_1.7 Al_0.3O₇: 0.1Eu²⁺, 0.1Mn²⁺ LED achieves good color rendering of over 85.     

Sol-gel growth of Gd2MoO6:Eu nanocrystalline layers on SiO2 spheres (SiO2@Gd2MoO6:Eu) and their luminescent properties

SiO₂@Gd₂MoO₆:Eu³⁺ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO₂@Gd₂MoO₆:Eu³⁺ core-shell phosphors. The XRD results demonstrate that the Gd₂MoO₆:Eu³⁺ layers on the SiO₂ spheres begin to crystallize after annealing at 600 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 600 nm), are not agglomerated, and have a smooth surface. The thickness of the Gd₂MoO₆:Eu³⁺ shells on the SiO₂ cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). The Eu³⁺ shows a strong PL luminescence (dominated by ⁵D₀-⁷F₂ red emission at 613 nm) under the excitation of 307 nm UV light. The PL intensity of Eu³⁺ increases with increasing the annealing temperature and the number of coating cycles.     

Synthesis and photoluminescence characteristics of (Sr, Ca)3B2O6:Eu for application in white light-emitting diodes

A series of yellow-green (Sr, Ca)₃B₂O₆:Eu phosphors have been synthesized using precursors prepared via a facile sol-gel route. The solid-solution phases crystallized to materials with the formula of Sr_3−x−yCa_xEu_yB₂O₆ with varied Ca²⁺ and Eu²⁺ contents. The emission peak centered at 540 nm under near-UV excitation exhibited a broad-band distribution in the range of 450-650 nm. The dependences of the luminescence intensity on the contents of Ca²⁺ substitution and Eu²⁺ dopant were also investigated. The composition in the host lattice sensitively affected the chromaticity index. Sr_1.21Ca_1.7Eu_0.09B₂O₆ (SCB:0.09Eu) was shown to possess the highest intensity and broadest emission band. Calcining temperature was shown to greatly influence the luminescent properties of SCB:0.09Eu. It is concluded that SCB:0.09Eu can be used as an efficient yellow-green phosphor for white light-emitting diodes (white LEDs) applications.     

New promising phosphors Ba3InB9O18 activated by Eu/Tb

Borate Ba₃InB₉O₁₈ (BIBO) has been adopted as a host material for phosphors for the first time. Lanthanide ions (Eu³⁺/Tb³⁺)-doped BIBO phosphors have been synthesized by solid-state reaction and luminescent properties investigated under ultravoilet (UV) excitation. For red phosphor BIBO:Eu, dominant emission peaking at 590 nm was attributed to ⁵D₀→⁷F₁ transition of Eu³⁺, which confirmed that the local site of Eu³⁺ occupied by In³⁺ ion in BIBO crystal lattice is at inversion symmetry center. Optimum Eu³⁺ concentration of BIBO:Eu under UV excitation with 227 nm wavelength is around 40%. The green phosphor BIBO:Tb showed bright green emission at 550 with 232 nm light excited and optimal of Tb³⁺ concentration measured in BIBO is about 8%. The corresponding luminescence mechanisms of Ln-doped BIBO (Ln=Eu³⁺/Tb³⁺) were analyzed. The luminescent intensity of Tb³⁺ can be significantly improved by co-doping of Bi³⁺ in the BIBO:Tb lattice. The likely reason was proposed in terms of the different interactions of the host lattice with these ions, and of these ions with each other.     

Effects of non-stoichiometry on crystallinity, photoluminescence and afterglow properties of Sr2MgSi2O7:Eu, Dy phosphors

Eu²⁺, Dy³⁺ co-doped Sr₂MgSi₂O₇ phosphors with deficient, stoichiometric or excess amounts of silicon are prepared by solid-state reaction. XRD and SEM results indicate that all the samples studied are found to be free from impurities and samples with SiO₂ excess possess better crystallinity and larger grain size. Photoluminescence reveals that the position of Eu²⁺ emission is not changed with various compositions. However, both photoluminescence intensity and afterglow properties are increased by an incorporation of excess SiO₂ and are decreased by SiO₂ deficiency. The thermoluminescence results show that the corresponding increase or decrease in afterglow is associated with trap density, but no change in trap depth. The underlying reason of photoluminescence and afterglow enhancement is discussed.     

Orange emission enhancement by energy transfer in Sr3Al2O5Cl2:Ce, Eu phosphor for solid-state lighting

Orange-emissive Ce³⁺/Eu²⁺ co-doped Sr₃Al₂O₅Cl₂ phosphors were synthesized by a solid-state reaction. The large overlap between the emission spectrum of blue Sr₃Al₂O₅Cl₂:Ce³⁺ and the excitation spectrum of orange Sr₃Al₂O₅Cl₂:Eu²⁺, and the shortening trend in lifetime of Ce³⁺ donors with increasing Eu²⁺ concentration in Sr₃Al₂O₅Cl₂:Ce³⁺, Eu²⁺ provide the strong evidence of energy transfer from Ce³⁺ to Eu²⁺ ions. It supports that the orange emission intensity of the optimal co-doped phosphor is 1.5 times stronger than that of single Eu²⁺-doped one. The Sr₃Al₂O₅Cl₂:Ce³⁺, Eu²⁺ phosphor is a promising orange-emitting phosphor for warm-white-light-emitting diode because of its effective excitation in the near ultraviolet range.     

Eu/Tb ions co-doped white light luminescence Y2O3 phosphors

Y₂O₃:Eu³⁺, Tb³⁺ phosphors with white emission are prepared with different doping concentration of Eu³⁺ and Tb³⁺ ions and synthesizing temperatures from 750 to 950 °C by the co-precipitation method. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicate that the crystallinity of the synthesized samples increases with enhancing the firing temperature. The photoluminescence spectra indicate the Eu³⁺ and Tb³⁺ co-doped Y₂O₃ phosphors show five main emission peaks: three at 590, 611 and 629 nm originate from Eu³⁺ and two at 481 and 541 nm originate from Tb³⁺, under excitation of 250-320 nm irradition. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu³⁺ and Tb³⁺ ions were induced into the Y₂O₃ lattice and the energy transfer from Tb³⁺→Eu³⁺ ions in these phosphors was found. The Commission International de l’Eclairage (CIE) chromaticity shows that the Y₂O₃:Eu³⁺, Tb³⁺ phosphors can obtain an intense white emission.