稀土钐离子可见荧光量子产率的精确测试与计算

采用积分球配以CCD光谱测试系统,在蓝色半导体发光二极管激发下,对Sm3 掺杂的低声子能量、高折射率铋碲酸盐玻璃的荧光光谱进行测试。实现了荧光发射特性绝对评价为目的的绝对光谱功率分布测定,为发光与激光材料荧光发射特性的精确测量与表征提供了一种准确方法。荧光测试系统由直径为25.4cm的积分球配以CCD探测器组成,通过标准卤素灯定标,辅助卤素灯校正积分球内环境变化,解析出样品的绝对光谱功率分布,并进一步计算出光量子数分布,求得荧光量子产率等荧光特征参量。测试与计算结果表明,对应可见区Sm3 四个特征发射峰,总荧光量子产率为7.55%。     

紫色发光二极管激发下钐掺杂的重金属硅酸盐玻璃的辐射通量与光通量(英文)

采用积分球测试系统配以内芯直径为400μm的功率光纤连接的CCD探测器,在紫色发光二极管的激发下,对Sm3+掺杂的重金属硅酸盐(CAS)玻璃的荧光光谱进行了表征,实现了以荧光发射特性绝对评价为目的绝对光谱功率分布测定,进一步求得了辐射通量,光通量等荧光特征参数。测试与计算结果表明,在整个可见光谱区域,总的辐射通量和光通量分别为712μW和12.1 mlm,其中Sm3+的4个特征发射峰的辐射通量和光通量分别为36μW和9.7 mlm,占可见区总量的5%和80%,其可见特征发射的总量子产率为2.3%。Sm3+掺杂CAS玻璃可见区多通道辐射跃迁的绝对光谱参数评估为照明和显示器件的研发提供了有益的参考依据。     

铈掺杂钆镓铝石榴石相玻璃陶瓷的光学及光谱参数

根据X射线衍射图谱对铈掺杂的钆镓铝石榴石相玻璃陶瓷的晶体结构进行分析,采用直径10英寸积分球结合CCD(charge coupled device)探测器系统,对蓝色半导体发光二极管激发下铈掺杂钆镓铝石榴石相玻璃陶瓷的荧光光谱进行测试,解析出样品发光的绝对光谱功率分布,推导出光量子数分布,求得荧光量子产率和组合白光的色坐标及其相关色温。结果表明,所调查的铈掺杂钆镓铝石榴石相玻璃陶瓷在蓝光LED激发下的荧光量子产率为29.2%,所获得组合白光的色坐标x=0.319,y=0.349,相关色温为6 086K。尽管该混晶陶瓷的荧光量子产率稍小于铈掺杂YAG玻璃陶瓷,但其与蓝光LED组合后发光的色温也明显低于后者,从而为舒适型LED照明玻璃陶瓷的进一步优化提供了新思路。     

Spectral and luminescent characteristics of trivalent lanthanide ions in a POCl3-SnCl4 inorganic solvent

We have measured the absorption and luminescence spectra of trivalent lanthanide ions (Pr³⁺, Sm³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, and Yb³⁺) in the visible and near-IR wavelength ranges in a POCl₃-SnCl₄ inorganic solvent. In terms of the Judd-Ofelt model, the oscillator strengths of absorption bands, the probabilities of radiative transitions, the luminescence branching coefficients, the lifetimes of excited states, and the luminescence quantum yields have been calculated. Possibilities of creating new laser media have been evaluated. A conclusion is drawn regarding the symmetry of the environment of trivalent lanthanide ions in the POCl₃-SnCl₄ solvent.     

Optical Spectroscopy of Sm3+ and Dy3+ Doped ZnO Nanocrystals

Sm³⁺ and Dy³⁺ ions doped hexagonal wurtzite ZnO nanocrystals were fabricated by a sol-gel method. The obtained ZnO nanocrystals were characterized using the X-ray diffraction, transmission electron microscopy, ultraviolet-visible reflectance spectra, and low-temperature luminescence spectroscopy. Intense and well resolved emission lines for Sm³⁺ and Dy³⁺ ions can be achieved via an energy transfer process from ZnO host to the dopants. It was found that the host sensitized emissions were more efficient than that of direct excitation for Sm³⁺ and Dy³⁺ ions. Moreover, multiple sites of Sm³⁺ and Dy³⁺ ions in ZnO nanocrystals were identified based on the low-temperature photoluminescence spectra.     

Optical properties of Sm-doped CaF2 bismuth borate glasses

Sm³⁺-doped calcium fluoride bismuth borate glasses were prepared and characterized optically and the oscillator strengths and Judd–Ofelt parameters for the glass containing 1.5 mol% of Sm₂O₃ were calculated. Density and optical absorption, transmission and the emission spectra were measured. The values of Judd–Ofelt parameters suggested an increase in the degree of asymmetry the local ligand field at Sm³⁺ sites. The optical band gap energy, band tailing parameter and Urbach's energy were calculated for all glass samples. It was found that with increasing the concentration of Sm₂O₃ content the values of the optical band gap energy decrease whereas Urbach's energy increases. Absorption and excitation spectra indicate that commercial UV and blue laser diodes, blue and bluish-green LEDs and Ar⁺ optical laser are powerful excitation sources for Sm³⁺ visible fluorescence in the glass.     

Energy transfer between Sm and Er in orthophosphate YPO4

The energy transfer between Sm³⁺ and Er³⁺ ions in yttrium orthophosphate is studied. This choice of ions is based on the possibility of quantum cutting processes and the host material is selected according to the position of the 5d bands of the Sm³⁺ ion. The Sm³⁺ and Er³⁺ doped and Sm³⁺, Er³⁺ co-doped YPO₄ have been synthesized. Spectroscopic studies were done in the ultraviolet and vacuum ultraviolet ranges. The energy transfer between Sm³⁺ and Er³⁺ is very efficient but it does not lead to Er³⁺ visible emission. Whatever the excitation wavelength, the emission of co-doped samples mainly occurs in the infrared range.     

CaS:Eu,Sm及其在农用转光膜上的应用原理

利用稀土直接掺杂工艺合成了一种“常光充能”型电子陷获材料CaS:Eu,Sm,它不仅具有CaS:Eu无机发光材料的荧光光谱特性,而且具有红外升频转换特性,可将0.8～1.6μm的红外光直接转换为～672nm的红光、量子效率高达76%,是一种优于CaS:Eu的光转换农膜添加剂.而共掺Eu²⁺、Sm³⁺和Cu⁺的CaS荧光粉有望成为一种性能优于光转换农膜添加剂CaS:Eu²⁺,Cu⁺、可人工模拟叶绿素吸收光谱的新型农用转光膜材料.     

Synthesis and photoluminescence properties of Sm-doped CaWO4 nanoparticles

The Sm³⁺-doped CaWO₄ nanoparticles were synthesized by hydrothermal method. The room temperature photoluminescence (PL) spectra of Sm³⁺-doped CaWO₄ nanoparticles doped with different Sm³⁺ concentrations under 405 nm excitation have been investigated. The PL spectra showed four strong emission peaks at 460, 571, 609, and 653 nm. The first emission peak at 460 nm could be due to a structural defect of the lattice, an oxygen-deficient WO₃ complex. The other three emissions at 571, 609, and 653 nm were due to the f-f forbidden transitions of the 4f electrons of Sm³⁺, corresponding to ⁴G_5/2→⁶H_5/2 (571 nm), ⁶H_7/2 (609 nm), and ⁶H_9/2 (653 nm), respectively. In addition, the optimum Sm³⁺ concentration in CaWO₄ nanoparticles for optical emission was determined to be 1.0%. The Sm³⁺⁴G_5/2→⁶H_7/2 (609 nm) emission intensity of Sm³⁺-doped CaWO₄ nanoparticles significantly increased with the increase of Sm³⁺ concentration, and showed a maximum when Sm³⁺ doping content was 1.0%. If Sm³⁺ concentration continued to increase, namely more than 1.0%, the Sm³⁺⁴G_5/2→⁶H_7/2 emission intensity would decrease. The present materials might be a promising phosphor for white-light LED applications.     

Quantum cutting in Gd<Subscript>2</Subscript>SiO<Subscript>5</Subscript>: Eu<Superscript>3+</Superscript> by VUV excitation

The emission and excitation spectra of Gd₂SiO₅∶Eu³⁺ were investigated using the VUV beam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results were discussed in the frame of visible quantum cutting process involved in Gd³⁺−Eu³⁺ system. Upon direct excitation into the⁶G _J states of Gd³⁺, two visible photon emissions from Eu³⁺ were observed. Cursory evaluation proved that Gd₂SiO₅∶Eu³⁺ is an efficient visible quantum cutter.     

Photon down-shifting by energy transfer from Sm3+ to Eu3+ ions in sol-gel SiO2-LaF3 nano-glass-ceramics for photovoltaics

95SiO₂?C5LaF₃ sol-gel derived nano-glass-ceramics single doped with Eu³⁺ or Sm³⁺ and codoped with both of them were successfully obtained. XRD measurements confirm the precipitation of LaF₃ nanocrystals after the ceramming process, with mean size ranging from 10 to 20?nm which increases with the thermal treatment temperature. The incorporation of rare-earth ions into precipitated LaF₃ nanocrystals was confirmed from luminescence spectra. Intense yellow-red emissions were detected under UV and blue light excitation in single and codoped samples. The effect of codoping with Eu³⁺ and Sm³⁺ ions and the energy transfer mechanism between them have been analyzed in order to increase the yellow-red emissions.     

Preparation and characterization of tunable YVO4: Bi, Sm phosphors

Yttrium vanadate phosphors co-doped with Bi³⁺- and Sm³⁺ ions have been prepared via the solid-state reaction as well as via the sol-gel method. The luminescence studies demonstrate the potential of the prepared phosphors as multi-color emitters, which can be achieved by adjusting the excitation wavelengths. The excitation spectra of Bi³⁺- and Sm³⁺ co-doped phosphors clearly revealed energy transfer from Bi³⁺ to Sm³⁺ ions. When the co-doped phosphors were excited at 254 nm, the emission from Bi³⁺ was dominant. Upon excitation at 365 nm, the emission from both Bi³⁺ and Sm³⁺ was detected. With 410 nm excitation, Sm³⁺ ions were selectively excited to yield intense red emission. It is shown that the prepared phosphors with optimal concentrations of Bi³⁺ and Sm³⁺ can be excited at 254, 365 and 410 nm to yield yellow, orange and red emissions, respectively.     

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.     

Tuning the Photometric Properties of Ternary Sm3+ Complexes Involving Mixed-Ligands

This research article deals with the synthesis of ternary Sm³⁺ complexes with 6,8-dichlorochromone-3-carboxaldehyde through solution-precipitation method. The photometric properties of resultant complexes were tuned by coordinating N-donor heterocyclic ligands with Sm³⁺ ion. The emission spectra, obtained in the visible region have been studied. Under optical excitation of 370 nm, the complexes displayed characteristic Sm³⁺-centered emission peaks at?~?563, 600 and 647 nm in solution as well as in powder state. The complexes showed thermal stability up to 175 °C. The complexes delivered quantum yield as high as 7.91% and longest emission lifetime of 0.564 ms. The color coordinates of the complexes, located in deep orange (in solution) and red (in powder) spectral region, matched well with the Society of Motion Picture and Television Engineers and European Broadcasting Union. The properties of complexes have been investigated to a significant extent due to their easy synthesis and potential applications as orange-red light emitter in a wide range of photonic applications such as display devices, OLEDs, dashboards, optical systems.

     

Spectral hole burning and fluorescence in femtosecond laser induced Sm-doped glasses

The femtosecond laser was used to irradiate sol-gel derived Sm³⁺-doped Al₂O₃-SiO₂ glasses, in which the Sm³⁺ was reduced into Sm²⁺ ions. The fluorescence line narrowing was applied to investigate the coordination sphere of the Sm²⁺ ion. The spectral hole burning was performed on ⁷F₀→⁵D₀ transition of the Sm²⁺. The depth and width of the burnt holes were ∼27% and ∼4 cm⁻¹ FWHM at 7 K, respectively. Hole spectra were stable up to room temperature. The hole-burning efficiency was superior to that of Sm²⁺ in H₂ treated glasses and comparable to that in X-ray in terms of hole-burning dynamics.     

Analysis of Energy Transfer and Concentration Quenching in Sm3+-Activated Borate GdB3O6 Phosphors by Means of Fluorescence Dynamics

This article reports on the optical properties of Sm³⁺-activated GdB₃O₆ phosphors based on the measurement of their photoluminescence spectra and luminescence decay curves. Energy transfer from Gd³⁺ to Sm³⁺ and the concentration quenching of the Sm³⁺ ion emission are investigated. From the photoluminescence spectra and decay curves, the energy transfer from Gd³⁺ to Sm³⁺ is confirmed. The concentration quenching of the Sm³⁺ ion emission can be ascribed to resonant cross-relaxation. The interaction between the Sm³⁺ ions is derived of the electric dipole–dipole type through fitting the data with the Inokuti-Hirayama model. The critical distances and energy transfer microparameter for the transfer processes are given. The decay curves of Sm³⁺⁴G_5/2 level exhibiting a buildup and decay process also confirm the energy transfer from Gd³⁺ to Sm³⁺ and between Sm³⁺ ions.     

Energy levels in YPO4:Ce3+,Sm3+ studied by thermally and optically stimulated luminescence

Energy-resolved optically stimulated luminescence (OSL) spectra and thermoluminescence (TL) glow curves of a powder sample of YPO₄:Ce³⁺,Sm³⁺ were measured to investigate the nature of the trapping centre and to locate its energy level relative to the valence and conduction bands of the YPO₄ host. The high-temperature glow peak could unequivocally be assigned to Sm²⁺ (thus Sm³⁺ acts as an electron trap). The trap depth of this centre, as derived from the OSL excitation spectra, is in good agreement with the Dorenbos model prediction. The OSL excitation spectra also reveal excited states of Sm²⁺ well below the conduction band. These excited states produce a broadening of the high-temperature TL glow peak and also cause the activation energy determined by the Hoogenstraten method to underestimate the trap depth.     

The dependence of luminescence on reduction of Sm2+ ions doped in lithium barium borate glasses

Sm³⁺-doped Li₂O–BaO–B₂O₃ glass was prepared by the conventional melt quenching method in air atmosphere. Sm²⁺ ions were obtained by two methods, i.e. heating the as-made glass in a reducing atmosphere and irradiating the sample under X-rays. The two obtained samples were investigated by luminescence spectra and lifetime measurements. It was found that the conversion of Sm³⁺→Sm²⁺ after X-ray irradiation is efficient in this borate glass. Photo-stability of Sm²⁺ ions was evaluated by the photo-bleaching method. Furthermore, thermo-luminescence was also measured. The different defects and the reduction mechanism of Sm²⁺ ions in this borate glass were discussed. This would be helpful to understand the reduction mechanism of Sm²⁺ ions in borate glasses.     

Optical spectra and excited state relaxation dynamics of Sm<Superscript>3+</Superscript> in Gd<Subscript>2</Subscript>SiO<Subscript>5</Subscript> single crystal

Single crystals of gadolinium orthosilicate Gd₂SiO₅ containing 0.5 at% and 5 at% of Sm³⁺ were grown by the Czochralski method. Optical absorption spectra, luminescence spectra and luminescence decay curves were recorded for these systems at 10 K and at room temperature. Comparison of optical spectra recorded in polarized light revealed that the anisotropy of this optically biaxial host affects the intensity distribution within absorption and emission bands related to transitions between multiplets rather than the overall band intensity. It has been found that among four bands of luminescence related to the ⁴G_5/2→⁶H_J (J=5/2–11/2) transitions of Sm³⁺ in the visible and near infrared region the ⁴G_5/2 →⁶H_7/2 one has the highest intensity with a peak emission cross section of 3.54×10⁻²¹ cm² at 601 nm for light polarized parallel to the crystallographic axis c of the crystal. The luminescence decay curve recorded for Gd₂SiO₅:0.5 at% Sm³⁺ follows a single exponential time dependence with a lifetime 1.74 ms, in good agreement with the ⁴G_5/2 radiative lifetime τ _rad=1.78 ms calculated in the framework of Judd-Ofelt theory. Considerably faster and non-exponential luminescence decay recorded for Gd₂SiO₅:5 at% Sm³⁺ sample was fitted to that predicted by the Inokuti-Hirayama theory yielding the microparameter of Sm³⁺–Sm³⁺ energy transfer C _da=1.264×10⁻⁵² cm⁶×s⁻¹.     

Photoluminescent properties of Sm-doped zinc oxide nanostructures

Sm³⁺-doped zinc oxide nanophosphors were synthesized by solution combustion method. The size of the ZnO:Sm³⁺ nanostructures ranges from 40-60 nm. The photoluminescence spectra of ZnO:Sm³⁺ nanostructures is different from that of pure ZnO. The emission spectra of ZnO:Sm³⁺ nanostructures show a strong narrow emission peak at 425 nm and weak peaks at 457, 472 and 482 nm when excited with 255 nm.