Luminescence of YAG doped with Eu,Yb, and Mn ions under VUV excitation

Hydrothermal synthesis has been successfully used to obtain fine-crystalline powders of yttrium aluminum garnet (YAG) doped with manganese ions and codoped with cerium and manganese ions. Using the method of high-temperature solid-state synthesis, ceramic specimens of YAG that contain europium and ytterbium ions have been obtained. In synthesized YAG:Eu and YAG:Yb ceramics, no luminescence that can be attributed to 5d-4f transitions in Eu²⁺ or Yb²⁺ ions has been detected, even though the scheme of energy levels of these ions constructed with respect to YAG energy bands indicates that there is a potential possibility of the occurrence of 5d-4f luminescence for Eu²⁺ ions in YAG. At room temperature, the luminescence spectrum of hydrothermally synthesized YAG doped with manganese ions consists of two broad bands with maxima at ～600 and ～750 nm and does not contain any narrow bands in the red or IR range. Therefore, the spectrum contradicts to the properties of the luminescence of Mn²⁺, Mn³⁺, or Mn⁴⁺ ions in YAG described in the literature, even though the obtained hydrothermal specimens can contain noticeable concentrations only of Mn³⁺ ions.     

Spectral properties of rare-earth ions in nanocrystalline YAG:Re (Re=Ce, Pr, Tb)

Bulk and nanoscale powders of YAG:Re (Re=Ce, Pr, Tb) were synthesized by solid-state and sol-gel method. The changes of spectra and energy level were studied. Compared with the bulk YAG:Re (Re=Ce, Pr, Tb) crystals, the lattice parameter of YAG:Re (Re=Ce, Pr, Tb) nanocrystals decreases. It is also found that the excitation peaks of 5d energy levels shift in nanocrystals. The physical reason for spectral and energy level changes is a comprehensive result from the shift of energy centroid of the 5d orbit, the Coulomb interaction between 4f and 5d electrons and the crystal field splitting of the 5d energy level.     

Luminescence characteristics of K2Ca2(SO4)3:Eu,Tb micro- and nanocrystalline phosphor

K₂Ca₂(SO₄)₃ microcrystalline pure, doped with Eu, Tb and co-doped with Eu, Tb was prepared by solid-state diffusion method. Nanoparticles of these phosphors were also prepared by the chemical co-precipitation method. The formation of the compounds was confirmed by XRD. The particle size was calculated by broadening of the XRD peaks using Scherrer's formula. The particle size of nanocrystalline powder material was approximately found to be around 20 nm. Thermoluminescence and photoluminescence were studied to see the effect of co-doping and particle size. Tb³⁺ co-doping decreases the intensity in the Eu²⁺ doped phosphor due to the energy transfer and multiple de-excitations through various radiative and non-radiative processes. The sensitivity of K₂Ca₂(SO₄)₃:Eu,Tb microcrystalline phosphor was around 15 times more than LiF-TLD 100 and 7 times more than CaSO₄:Dy. A high temperature peak (615 K) was observed in case of the nanoparticles, which was attributed to a particle size induced phase transition. This was confirmed by differential scanning calormetry measurements. The decrease in the sensitivity in case of nanoparticles is attributed to the particle size effect i.e. volume to surface ratio. Theoretical analysis of the glow curves was done by glow curve convolution deconvolution method to calculate trapping parameters of various peaks.     

Micro-Meter Size Organogelator with Tri-Color Luminescence (Blue, Green and Red) Activated by Dy3+, Tb3+ and Eu3+ ions

The preparation of a novel type of low-molecular-weight amphiphilic organogelator bearing three long 14-alkyl chains and hydrophilic oligo(oxyethylene) groups was described. Ultra-violet absorption and fluorescence spectra give evidence of the energy transfer between organic ligands to lanthanide ions. Characteristic green, blue and red luminescence of the organogels were obtained and interesting emission properties of terbium, dysprosium and europium ions were unexpectedly observed at the first time during the order-disorder phase transition point (29 °C).     

Luminescent and scintillation properties of YAG:Dy and YAG:Dy,Ce single crystalline films

The paper is devoted to investigation of the luminescent properties of Dy³⁺ and Dy³⁺-Ce³⁺ doped single crystalline films (SCF) grown by LPE method from PbO–B₂O₃ flux. We have found that the YAG:Dy and YAG:Dy,Ce SCFs possess bright cathodoluminescence in the visible range and good scintillation figure of merit. For this reason LPE grown YAG:Dy and YAG:Dy,Ce SCF are proposed for different applications, namely, as cathodoluminescence screens or screens for microimaging. The Dy³⁺ co-doping can be also proposed for improvement of the scintillation efficiency of the Ce³⁺ doped garnet compounds in the SCF form due to Dy³⁺→ Ce³⁺ energy transfer and removing the trap related centers in the above RT range.     

KAlF4：Ce,Tb磷光体的发光特性及Ce^3＋对Tb^3＋的敏化作用

采用溶液反应法和高温固相反应法合成了ＫＡ１Ｆ４基质化合物及ＫＡ１Ｆ：Ｃｅ，Ｔｂ磷光体，测定了磷光体的激发光谱和发射光谱，研究了在碱金属氟铝酸盐基质中Ｃｅ＾３＋对Ｔｂ＾３＋的能量传递，根据Ｃｅ＾３＋，Ｔｂ＾３＋在ＫＡｌＦ４中的能级关系，分析了其发光特性和Ｃｅ＾３＋对Ｔｂ＾３＋能量传递过程。     

Eu和Dy掺杂BaAl12O19长余辉发光性能研究

采用高温固相法在不同的气氛条件下合成了BaAl12O19:Eu2+/Eu3+,Dy3+发光材料。X射线衍射(XRD)表明:实验得到了纯净的BaAl12O19相结构,Eu和Dy的掺入并未改变相结构。通过比较发现,Eu和Dy掺杂后导致XRD衍射峰向高角度有微小移动,显示Eu和Dy取代晶格中Ba后使面间距发生变化。发射光谱表明:在不同条件下合成的样品都存在Eu2+的4f65d1→4f7之间的宽带跃迁;空气气氛下合成的样品中Eu2+的宽带跃迁的存在表明样品中发生了自还原现象。Dy3+的加入使样品发光增强,同时样品具备了长余辉特性。还原气氛下合成的Eu和Dy共掺样品的余辉衰减和热释光研究表明所得样品具有良好的室温和高温长余辉性能。     

(La,Ce,Tb)BO3的合成及光谱性质

采用高温固相法合成了(La,Ce,Tb)BO₃绿色发光粉,并对该发光粉进行了XRD和SEM分析。结果表明:(La,Ce,Tb)BO₃的晶体结构和LaBO₃相同,Ce³⁺、Tb³⁺的掺入并没有改变晶体的结构,发光粉颗粒大小均匀,形貌规则,粒度在5 μm左右。研究了(La,Ce,Tb)BO₃的光谱性质,在(La,Ce,Tb)BO₃的发射和激发光谱中除了有Tb³⁺的特征发射和激发峰外,还有Ce³⁺的特征发射和激发峰。比较了(La,Ce)BO₃发射光谱和(La,Tb)BO₃的激发光谱,两者存在重叠,这为Ce³⁺→Tb³⁺的能量传递提供了条件。将(La,Ce,Tb)BO₃的发射光谱与商品粉(La,Ce,Tb)PO₄进行比较,两者的发射主峰都在541 nm处, (La,Ce,Tb)BO₃在489 nm处的峰位稍有红移,通过计算表明,(La,Ce,Tb)BO₃的发光亮度达到商品粉(La,Ce,Tb)PO₄的94.7%。因此,(La,Ce,Tb)BO₃是一种很有应用前景的绿色发光粉。     

Y(BO3,PO4):Ce,Tb,Gd的发光特性研究

用ＢＰＯ４和稀土氧化为原料,通过单片灼烧,首次合成了铈、铽、钆共激活的硼磷钇绿色荧光粉,利用发射光谱和激发光谱研究了基质中Ｃｅ＾３＋、Ｔｂ＾３＋、Ｇｄ＾３＋的发光以及它们之间的相互作用结果表明在铈、铽或钆、铽的双掺杂体系中存在Ｃｅ＾３＋→Ｔｂ＾３＋、Ｇｄ＾３＋→Ｔｂ＾３＋的能量传递,而在铈、钆双掺杂的体系中却观察到了Ｃｅ＾３＋和Ｇｄ＾３＋离子之间的竞争吸收和独自发射。在铈、铽共激活的硼磷民体系中掺     

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.     

Luminescence studies on SrMgAl10O17:Eu, Dy phosphor crystals

Using urea as fuel, SrMgAl₁₀O₁₇:Eu, Dy phosphor was prepared by a combustion method. Its luminescence properties under ultraviolet (UV) excitation were investigated. Pure SrMgAl₁₀O₁₇ phase was formed by urea-nitrate solution combustion synthesis at 550 °C. The results indicated that the emission spectra of SrMgAl₁₀O₁₇:Eu, Dy has one main peak at 460 nm and one shoulder peak near 516 nm, which are ascribed to two different types of luminescent Eu²⁺ centers existing in the SrMgAl₁₀O₁₇ matrix crystal. The blue luminescence emission of SrMgAl₁₀O₁₇:Eu phosphors was improved under UV excitation by codoping Dy³⁺ ions. The SrMgAl₁₀O₁₇:Eu phosphors showed green afterglow (λ=516 nm) when Dy³⁺ ions were doped. Dy³⁺ ions not only successfully play the role of sensitizer for energy transfer in the system, but also act as trap levels and capture the free holes in the spinel blocks.     

激发波长和带宽对Ce/Tb/Eu共掺发光玻璃发光性质的影响

采用双高斯函数拟合不同中心波长和带宽的LED芯片光谱,并根据荧光分光光度计的测量结果推算不同LED芯片激发下的Ce/Tb/Eu共掺发光玻璃的发射光谱和色温。结果表明,当芯片带宽不变,中心波长从370 nm右移到378 nm时,Ce/Tb/Eu共掺发光玻璃色温逐渐下降。当芯片中心波长不变,带宽从10 nm增加到25 nm时,Ce/Tb/Eu共掺发光玻璃的色温变化与中心波长有关。在芯片发光稳定的前提下,带宽变化对Ce/Tb/Eu共掺发光玻璃色温的影响小于中心波长改变的影响,故当Ce/Tb/Eu共掺发光玻璃应用于LED发光时,需优先选择芯片的中心波长。     

Luminescence of KCaSO4Cl:X, Y (X=Eu or Ce; Y=Dy or Mn) halosulfate material

Polycrystalline KCaSO₄Cl:Eu, Dy, KCaSO₄Cl:Ce, Dy and KCaSO₄Cl:Ce, Mn phosphors prepared by a solid state diffusion method have been studied for its photoluminescence (PL) characteristics. The presence of two overlapping bands at around 400 and 450 nm in the PL emission spectra of the phosphor suggests the presence of Eu²⁺ in the host compound occupying two different lattice sites. The effects of co-doping on the photoluminescence (PL) characteristics of KCaSO₄Cl:Eu or Ce phosphors have been studied. The decrease in peak intensity of the phosphor on co-doping it with Dy gives an insight into the emission mechanism of the phosphors, which involves energy transfer from Eu²⁺→Dy³⁺, Ce³⁺→Dy³⁺ and Ce³⁺→Mn²⁺.     

Luminescence properties of Ba2NaNb5O15 crystals activated with Sm, Eu, Tb or Dy ions

Single crystals of Ba₂NaNb₅O₁₅ (BNN) singly doped with Sm³⁺, Eu³⁺, Tb³⁺ or Dy³⁺ have been grown by means of the flux growth method. Their visible emission and excitation spectra and the decay profiles of the luminescence have been measured at room temperature. All spectral features are significantly inhomogeneously broadened in consequence of the structural disorder of the host and of the doping mechanisms. The analysis of the observed spectra allows formulating an hypothesis about the site occupancy of the active ions in the BNN lattice.     

水热法制备LaF3:Ce,Tb纳米荧光粉及发光性质研究

利用水热法制备了LaF3∶Ce,Tb纳米荧光粉,分别用XRD,TEM和发光光谱等测试手段对粉末的物相、形貌、发光性质进行了研究.XRD和TEM结果表明:所得的纳米荧光粉粒度均匀、结晶完好,呈规则的六边形形状,颗粒平均尺寸为30 nm,掺人Ce3 和Tb3 ,杂质后晶格结构没有变化.发光光谱的测试表明:Ce3 呈现其宽带发射;Tb3 呈现其特征绿色发射,最强峰位于544 nm处.Ce3 的掺入有效敏化了Tb3 的发光,通过进一步光谱分析证实了在LaF3∶Ce,Tb体系中存在Ce3 →Tb3 的能量传递过程.当Ce3 和Tb3 掺杂摩尔浓度分别为35 mol%和5 mol%时具有最强荧光发射.制备的样品无需煅烧即可获得比体相材料高2倍的荧光,也高于优化条件下煅烧样品的荧光.     

稀土离子Ce,Tb掺杂硼磷酸锶荧光粉的发光性质

采用高温固相法合成了2SrO·0.25B₂O₃·0.75P₂O₅:RE³⁺(RE=Ce,Tb)荧光粉。研究了其中Ce³⁺,Tb³⁺的光谱性质,Ce³⁺和Tb³⁺共掺杂时的能量传递效率,以及Ce³⁺和Tb³⁺的动力学过程。发现在共掺杂的样品中,Tb³⁺的⁵D₄→⁷F₅绿色发射比Tb³⁺单掺杂样品中的绿色发射有显著的提高。当Tb³⁺的含量从1%增加到8%时,Ce³⁺→Tb³⁺的能量传递效率逐渐增加至70%。通过动力学研究,在Ce³⁺和Tb³⁺共掺杂的样品中,提高Tb³⁺的浓度,Ce³⁺的寿命减小。此外,Ce³⁺离子寿命的倒数与Tb³⁺的浓度之间很好地符合线性函数关系,经过拟合Ce³⁺离子的电子跃迁速率和Ce³⁺→Tb³⁺的能量传递速率分别为5.1×10^-2和1.34ns^-1·mol^-1。Tb³⁺的⁵D₄→⁷F₅跃迁的衰减曲线很好地遵守指数式衰减,并且随着Ce³⁺的掺杂浓度提高,Tb³⁺的⁵D₄→⁷F₅寿命增加。结果表明在共掺杂的2SrO·0.25B₂O₃·0.75P₂O₅材料中存在Ce³⁺到Tb³⁺的有效能量传递,这种材料在541nm处有着较强的绿光发射,所以将在发光以及显示领域有潜在的应用前景。     

YAG:Ce3+的合成与光谱性能研究

采用共沉淀法合成了YAGCe3+(Y3Al5O12Ce3+)光致发光荧光粉并测定了其激发光谱、发射光谱及粒度对发光强度的影响.结果表明,YAGCe3+荧光粉激发光谱为双峰结构,两主峰分别位于近紫外和可见光区,发射光谱为宽峰,峰值为550nm.X射线衍射(XRD)分析表明该发光粉为纯YAG晶相.