Luminescence of Ce and Pr doped Sr2Mg(BO3)2 under VUV-UV and X-ray excitation

This report presents the luminescence properties of Ce³⁺ and Pr³⁺ activated Sr₂Mg(BO₃)₂ under VUV-UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm⁻¹ (i.e. 214, 224, 240, 261 and 336 nm) for Ce³⁺ in the host lattice. The doublet Ce³⁺ 5d→4f emission bands were found at about 25 840 and 24 096 cm⁻¹ (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce³⁺ in Sr₂Mg(BO₃)₂ were investigated. For Pr³⁺ doped samples, the lowest 5d excitation band was observed at about 42017 cm⁻¹ (238 nm), a dominant band at around 35714 cm⁻¹ (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce³⁺ and Pr³⁺ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr_1.86Ce_0.07Na_0.07Mg(BO₃)₂ and Sr_1.82Pr_0.09Na_0.09Mg(BO₃)₂ at RT, respectively.     

Luminescence studies on ZnO-P2O5 glasses doped with Gd2O3:Eu nanoparticles and Eu2O3

Zinc phosphate glasses doped with Gd₂O₃:Eu nanoparticles and Eu₂O₃ were prepared by conventional melt-quench method and characterized for their luminescence properties. Binary ZnO-P₂O₅ glass is characterized by an intrinsic defect centre emission around 324 nm. Strong energy transfer from these defect centres to Eu³⁺ ions has been observed when Eu₂O₃ is incorporated in ZnO-P₂O₅ glasses. Lack of energy transfer from these defect centres to Eu³⁺ in Gd₂O₃:Eu nanoparticles doped ZnO-P₂O₅ glass has been attributed to effective shielding of Eu³⁺ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between the luminescent centre and Eu³⁺ ions. Both doped and undoped glasses have the same glass transition temperature, suggesting that the phosphate network is not significantly affected by the Gd₂O₃:Eu nanoparticles or Eu₂O₃ incorporation.     

Ce3+对Er3+/Yb3+共掺TeO2-WO3-ZnO玻璃发光性能的影响

在Er³⁺/Yb³⁺共掺TeO₂-WO₃-ZnO玻璃中引入Ce³⁺，研究了Ce³⁺对Er³⁺1.5μm发射性能及其上转换发光性能的影响。结果表明，随Ce³⁺浓度的增加Er³⁺1.5μm波段的荧光强度先增强后降低，优化的Ce³⁺掺杂浓度在2.07×10²⁰/cm³左右；1.5μm波段的荧光寿命则随Ce³⁺浓度的增加有轻微降低，从3.4ms降到3.0ms，但Ce³⁺浓度的增加对1.5μm波段的荧光半高宽基本无影响；Er³⁺/Ce³⁺间的交叉弛豫Er³⁺(⁴I_11/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_13/2)+Ce³⁺(²F_7/2)使玻璃的上转换发光强度大大降低，但在过高的Ce³⁺浓度下，Er³⁺/Ce³⁺间的另一交叉弛豫Er³⁺(⁴I_13/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_15/2)+Ce³⁺(²F_7/2)则使Er³⁺⁴I_13/2能级粒子数减少，导致1.5μm波段荧光强度和荧光寿命降低. 关键词： 碲钨酸盐玻璃 发光性能 3+离子')" href="#">Er³⁺离子 3+离子')" href="#">Ce³⁺离子 交叉弛豫     

Ce3+对Er3+/Yb3+共掺氟磷酸盐玻璃光谱性质的影响

研究了能量接受离子Ce³⁺对Er³⁺上转换发光强度以及Er³⁺在1.5μm附近波段发光性能参数的影响，并从能量匹配及能级结构角度出发对Er³⁺/Ce³⁺间的能量转移机制进行了分析.分析认为，⁴I_11/2能级的Er³⁺通过无辐射能量转移把能量传递给²F_5/2能级的Ce³⁺关键词： 氟磷酸盐玻璃 光谱性质 光纤放大器 3+和Ce³⁺')" href="#">Er³⁺和Ce³⁺     

Low temperature quenching and high efficiency Tm, La or Tb co-doped CaSc2O4:Ce phosphors for light-emitting diodes

Low temperature quenching and high efficiency CaSc₂O₄:Ce³⁺ (CSO:Ce³⁺) phosphors co-doped with Tm³⁺, La³⁺ and Tb³⁺ ions were prepared by a solid state method and the phase-forming, morphology, luminescence and application properties of these phosphors were investigated. The results showed that co-doping of Tm³⁺, La³⁺ and Tb³⁺ ions can improve the luminescence properties and decrease temperature quenching of CSO:Ce³⁺ phosphor remarkably. High efficiency green-light-emitting diodes were fabricated with the prepared phosphors and InGaN blue-emitting (∼460 nm) chips. The good performances of the green-light-emitting LEDs made from co-doped CSO:Ce³⁺ phosphors confirm the luminescence enhancement and indicate that Tm³⁺, La³⁺ and Tb³⁺ co-doped CSO:Ce³⁺ phosphors are suitable candidates for the fabrication of high efficiency white LEDs.     

Yb3+敏化的Er3+/Ho3+共掺碲酸盐玻璃的上转换发光研究

用高温熔融法制备了系列Er³⁺/Yb³⁺共掺，Ho³⁺/Yb³⁺共掺，和Er³⁺/Yb³⁺/Ho³⁺三掺碲酸盐玻璃，在975nm激光抽运下三种掺杂玻璃中都出现了较强的绿光和红光上转换.研究了Yb³⁺离子对Er³⁺和Ho³⁺离子上转换发光强度的影响以及Yb³⁺→Er关键词： 3+/Yb³⁺/Ho³⁺共掺')" href="#">Er³⁺/Yb³⁺/Ho³⁺共掺 碲酸盐玻璃 光谱性质 上转换     

Optical spectroscopy of Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12 doped with Pr

The silicates Ca₃Sc₂Si₃O₁₂, Ca₃Y₂Si₃O₁₂ and Ca₃Lu₂Si₃O₁₂, both undoped and doped with Pr³⁺ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca₃Sc₂Si₃O₁₂:Pr³⁺ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca₃Y₂Si₃O₁₂:Pr³⁺ and Ca₃Lu₂Si₃O₁₂:Pr³⁺ show features attributed to emission from two distinct sites accommodating the Pr³⁺ dopant. The decay kinetics of the Pr³⁺ 5d-4f emission in Ca₃Sc₂Si₃O₁₂:Pr³⁺ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence.     

Photoluminescence characterization of Ce and Dy doped Li2CaGeO4 phosphors

Ce³⁺ and Dy³⁺ activated Li₂CaGeO₄ phosphors were prepared by a solid-state reaction method, and characterized by XRD (X-ray diffraction) and photoluminescence techniques. The characteristic emission bands of Dy³⁺ due to ⁴F_9/2→⁶H_15/2 (blue) and ⁴F_9/2→⁶H_13/2 (yellow) transitions were detected in the emission spectra of Li₂CaGeO₄:Dy³⁺. Ce³⁺ broad band emission was observed in Li₂CaGeO₄:Ce³⁺ phosphors at 372 and 400 nm due to 5d→4f transition when excited at 353 nm. Co-doping of Ce³⁺ enhanced the luminescence of Dy³⁺ significantly and concentration quenching occurs when Dy³⁺ is beyond 0.04 mol%. White-light with different hues can be realized by tuning Dy³⁺ concentration in the phosphors.     

Temperature-dependent photoluminescence properties of (Y, Lu)3Al5O12:Ce phosphors for white LEDs applications

The effects of the excitation wavelength, Ce³⁺ concentration and chemical substitution on the thermal quenching of Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) phosphors were investigated over a temperature range from 30 to 250 °C. The quenching behavior exhibits a complex dependence on the excitation wavelength and Ce³⁺ concentration, which can be attributed to temperature-dependent absorption strength of the different f-d absorption bands and thermally activated concentration quenching with or without energy migrations between Ce³⁺ ions, respectively. With increasing Lu³⁺content the luminescence of (Y, Lu)₃Al₅O₁₂:Ce³⁺ phosphors shows a pronounced blueshift, and simultaneously the temperature quenching is obviously improved due to a decrease in Stokes shift.     

Upconversion properties of Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glasses

The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb^3＋/Er^3＋ is discussed in detail, and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb^3＋/Er^3＋ is also studied, The luminescence intensity increases with the ratio of Yb^3＋/Er^3＋ increasing. The ratio of Yb^3＋/Er^3＋ plays a more important role than the concentration of Er^3＋ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb^3＋/Er^3＋ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.     

Luminescence enhancement in (Nd+Ce) doped SiO2 : Al2O3 sol–gel glasses

An enhancement in NIR luminescence from Nd³⁺-doped Ce³⁺ co-doped SiO₂+Al₂O₃ sol–gel glasses has been observed. The lasing transition (⁴F_3/2→⁴I_11/2) at 1072 nm from the dual rare-earth Nd³⁺+Ce³⁺-doped glasses has shown an emission strength of about five times that of the single rare-earth ion Nd³⁺-doped glass. From the measurement of lifetimes of the transition at 1072 nm, the transfer rate (W_tr), critical distance (R₀) and energy transfer efficiency (η) of the neodymium glasses have been calculated.     

Ce3+ 掺杂高密度氧化物玻璃的闪烁性能研究

用高温熔融法制备了以SiO₂-B₂O₃-Al₂O₃-Gd₂O₃为基质系统Ce³⁺掺杂的玻璃样品, 测试样品的密度、紫外——可见透射光谱、紫外激发光谱和主要的闪烁性能, 并且把一部分闪烁性能和PbWO晶体及BGO晶体做比较. 着重研究了不同Ce³⁺掺杂浓度与Gd³⁺ 离子的含量对玻璃样品闪烁性能的影响规律. 结果表明: 玻璃样品具有较大的密度; 样品的X射线激发发射光谱发射峰位置都在390 nm左右, 当Ce³⁺ 离子的掺杂浓度为1.0 mol%(摩尔分数)、Gd₂O₃含量为15 mol%时, 玻璃样品的发光峰强度达到BGO晶体发光强度的90%; 同样验证了Ce³⁺ 离子具有浓度猝灭效应; Gd³⁺可以敏化Ce³⁺离子发光, 但是Gd³⁺离子到达一定浓度时, 反而会产生猝灭效应, 降低了Ce³⁺ 离子的发光. Ce³⁺ 离子掺杂SiO₂-B₂O₃-Al₂O₃-Gd₂O₃系统的闪烁玻璃有望替代闪烁晶体广泛应用于高能物理中.     

Effect of Ce on the spectroscopic properties in Er doped TeO2-GeO2-Nb2O5-Li2O glasses

The Ce³⁺ ion was introduced into Er³⁺ doped TeO₂-GeO₂-Nb₂O₅-Li₂O (TGNL) glass to improve the 1.5 μm fluorescence characteristics. As increasing of Ce³⁺ concentration, the lifetime of Er³⁺:⁴I_11/2 level is shortened form 360 to 225 μs, while the Er³⁺:⁴I_13/2 level remains unchanged. Accordingly, the upconversion fluorescence (blue, green and red) was quenched. Improved 1.5 μm emission is obtained and the reason is ascribed to the increase of nonradiative rate between the ⁴I_11/2 and ⁴I_13/2 level of the Er³⁺ ions.     

Ce$lt;sup$gt;3+$lt;/sup$gt;在LiBaBO$lt;sub$gt;3$lt;/sub$gt;中的发光特性及晶体学格位

采用固相法制备了LiBaBO₃：Ce³⁺发光材料.测得LiBaBO₃：Ce³⁺材料的发射光谱为一不对称的单峰宽谱,主峰位于440 nm;监测440 nm发射峰,可得其激发光谱为一主峰位于370 nm的宽谱.利用van Uitert公式计算了Ce³⁺取代LiBaBO₃中Ba²⁺时所占晶体学格位,得出438 nm发射带归属于九配位的Ce³⁺发射,而469 nm发射带起源于八配位的Ce³⁺发射.研究了Ce³⁺浓度对LiBaBO₃：Ce³⁺材料发光强度的影响,结果显示,随Ce³⁺浓度的增大,发光强度呈现先增大后减小的趋势,Ce³⁺浓度为3mol%时强度最大,造成其浓度猝灭的原因为电偶极-偶极相互作用.引入Li⁺,Na⁺或K⁺可增强LiBaBO₃：Ce³⁺材料的发射强度.利用InGaN管芯（370 nm）激发LiBaBO₃：Ce³⁺材料,获得了很好的蓝白光发射,色坐标为（x=0.291,y=0.297）. 关键词： 白光发光二极管 3：Ce³⁺')" href="#">LiBaBO₃：Ce³⁺ 晶体学格位 发光特性     

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.     

Upconverted VUV luminescence of Nd and Er doped into LiYF4 crystals under XeF-laser excitation

The upconverted VUV (185 nm) and UV (230 and 260 nm) luminescence due to 5d-4f radiative transitions in Nd³⁺ ions doped into a LiYF₄ crystal has been obtained under excitation by 351/353 nm radiation from a XeF excimer laser. The maximum upconversion efficiency, defined as the ratio of intensity for 5d-4f luminescence to overall intensity for 5d-4f and 4f-4f luminescence from the ⁴D_3/2 Nd³⁺ level, has been estimated to be about 70% under optimal focusing conditions for XeF laser radiation. A redistribution of intensity between three main components of 5d-4f Nd³⁺ luminescence is observed under changing the excitation power density, which favors the most long-wavelength band (260 nm) at higher excitation density level. The effect is interpreted as being due to excited state absorption of radiation emitted. The upconverted VUV and UV luminescence from the high-lying ²F(2)_7/2 4f level of Er³⁺ doped into a LiYF₄ crystal has also been obtained under XeF-laser excitation the most intense line being at 280 nm from the spin-allowed transition to the ²H(2)_11/2 4f level of Er³⁺, but the efficiency of upconversion for Er³⁺ emission is low, less than 5%.     

Heat-treatment-induced luminescence degradation in Tb-doped CePO4 nanorods

CePO₄:Tb nanorods were synthesized via a simple wet-chemical route. The as-synthesized CePO₄:Tb nanorods present high photoluminescence efficiency due to an efficient energy transfer form Ce³⁺ to Tb³⁺. However, heat treatment at 150 °C in air leads to a significant decrease of photoluminescence. X-ray photoelectron spectroscopy and excitation spectra revealed the oxidation of Ce³⁺ to Ce⁴⁺ in the heat-treatment process, which should be responsible for significant photoluminescence degradation due to the breakage of Ce³⁺→Tb³⁺ energy transfer. This conclusion is further supported by atmosphere and size effects of photoluminescence of CePO₄:Tb under the heat treatment.     

Luminescence of La3F3[Si3O9]:Ce

The luminescence properties of Ce³⁺ in La₃F₃[Si₃O₉] are reported. Excitation and emission bands corresponding to 4f¹→5d¹ transitions of Ce³⁺ were identified. The center of gravity of the 5d states lies at remarkable high energy (43.2×10³ cm⁻¹) for Ce³⁺ in a silicate compound. This high value is attributed to the combined oxygen/fluoride coordination of the Ce³⁺ ion. Emission from the lowest 4f5d level to the ²F_5/2 and ²F_7/2 levels was found at 32.4×10³ and 30.4×10³ cm⁻¹. These results are compared with literature data on silicates and fluorides. From the values found for Ce³⁺, predictions are made for the positions of the 4f5d bands of Pr³⁺ and Er³⁺ in La₃F₃[Si₃O₉]. For both ions, it is concluded that in this host lattice emission is expected from high lying 4fⁿ energy levels.     

Luminescence of Mn ions in Tb3Al5O12 garnet

The paper is dedicated to investigation of the Mn²⁺ luminescence in Tb₃Al₅O₁₂ (TbAG) garnet, as well as the processes of excitation energy transfer between host cations (Tb³⁺ ions) and activators (Mn²⁺ and Mn²⁺-Ce³⁺ pair ions) in single crystalline films of TbAG:Mn and TbAG:Mn,Ce garnets which can be considered as promising luminescent materials for conversion of LED's radiation. Due to the effective energy transfer between TbAG host and activator, Mn²⁺ ions in TbAG possess the bright orange luminescence in the bands peaked at 595 nm with a lifetime of 0.64 ms which are caused by the ⁴T₁→⁶A₁ radiative transitions. The simultaneous process of energy transfer is realized in TbAG:Mn,Ce: (i) from Tb³⁺ to Mn²⁺ ions; (ii) from Tb³⁺ cations to Ce³⁺ ions and then partly to Mn²⁺ ions through Tb³⁺ ion sublattice and Ce-Mn dipole-dipole interaction.     

Infrared-excited bright green and red luminescence in La3Ga5.5Ta0.5O14 doped with erbium and ytterbium

Bright green (at 525 and 550 nm) and red (at 660 nm) luminescence in Er:Yb:La₃Ga_5.5Ta_0.5O₁₄ (LGT) powder synthesized by solid state reaction was obtained by pumping at 936 nm. Yb³⁺-Er³⁺ energy transfer processes accounting for population of the ²H2_11/2, ⁴S_3/2 and ⁴F_9/2 Er³⁺ levels are discussed. The dependence of ratio between the intensities of the green and red luminescence on pump intensity is analyzed. The rather high quantum efficiency (58%) of the (⁴S_3/2, ²H2_11/2) Er³⁺ emitting level recommends LGT doped with erbium and ytterbium for upconversion applications.