Preparation and Upeonversion Lumineseenee ofNanoerystailine Gd2O3： Er^3＋, Yb^3＋

Nanocrystalline Gd1.77Yb0.2Er0.03O3 samples were prepared by combustion and precipitation methods. Structures and upconversion luminescence properties of samples were studied. The results of XRD show that all samples are cubic structure, the average crystallite size could be calculated as 23 nm and 39 nm, respectively. The lattice constants were obtained. The FT-IR spectra were measured to investigate the vibrational feature of the samples. Upconversion luminescence spectra of samples under 980 nm laser excitation were investigated. The strong red emission of samples were observed, and attributed to 4F9/2→4I152 transitions of Er^3＋ ions, the emission intensity for sample synthesized by precipitation method is stronger compared to that of combustion method. The possible upconversion luminescence mechanisms in nanocrystalline Gd1.77Yb0.2Er0.03O3 were discussed.     

Soft chemical synthesis and luminescence properties of red long-lasting phosphors Y202S：Sm3＋

Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy （SEM） results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y202S：Sm3＋ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G5/2 →6H5/2, 4G~/2 →6H7/2, 4G5/2 →6H9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.     

Preparation and Luminescent Properties of Eu^3＋ Doped Calcium Phosphate Nanocrystalline

The nanocrystalline Eu^3＋ doped calcium phosphate was prepared by calcining precursors, which were got by precipitation method combined with ultrasound treatment and some polysaccharide. The existence of Eu^3＋ inhibited the reaction of Na^＋ ion and SO4^2- radical with apatite and resulted in the transformation of HAP to β- TCP by replacing the calcium ions. The strongest excitation peak was at 393 nm, and other lower peaks were at 361 nm, 375 nm, 381 nm, 418nm. The strongest emission spectrum appeared at about 618nm. The emission peak （579 nm） showed that Eu^3＋ ions distributed on Ca^2＋ sites of the apatitic structure.     

La , Li＋ Precipitation processes and luminescence properties of ZnO： 3＋ nanoparticles

ZnO:La3+ ,Li+ nanoparticles were successfully prepared by co-precipitation, citric acid-assisted co-precipitation, co-precipitation combined solid-state reaction and thermal decomposition method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectrophotometry were employed to characterize the crystal phases, particle sizes and luminescence properties of the as-prepared nanopowders. The results indicate that all the prepared samples crystallize in a hexagonal wurtzite structure. The ZnO:La 3+ ,Li+ prepared by citric acid-assisted co-precipitation method has a particle size of about 80 nm, which is the smallest among all the samples. Fluorescence (FL) spectra of all samples exhibit three typical emissions: a violet one centered at around 400 nm, blue around 450 nm and 466 nm, and weak green near 520 nm. But the samples prepared by co-precipitation method show a strong and wide green light emission located at about 500 nm. The ZnO:La 3+ ,Li+ nanoparticles synthesized by the co-precipitation method demonstrate relatively the strongest emission intensity.     

One new photon avalanche phenomenon of Er^3＋ at 976 nm excitation

A photon avalanche phenomenon was observed in Er^3＋ and Li^ ＋ eodoped ZnO nanocrystals at room temperature under excitation around 976 nm. When the excitation power was over 120 mW/mm^2 , we found that the upconversion of red emission was generated by a four-photon absorption process and might be caused by intense interaction between neighboring Er^3 ＋ ions ： ^4 F7/2 ＋ ^4 I11/2 → 2^4 F9/2. When the excitation power was over the threshold of 240 mW/mm^2, the green emission avalanche upconversion was generated through an excitedstate absorption process ： ^4 F9/2 ＋ photon →^2 H9/2. The study extends the knowledge of this ion to a wider range of upconversion application.     

Infrared-to-green upconversion properties of Er^3＋/Yb^3＋ co-doped TeO2-TiO2-K2O glasses upon excitation with 976 nm lasers diode

The energy transfer and upconversion of Er^3＋/Yb^3＋ co-doped TeO2-TiO2-K2O glasses upon excitation with 976 nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion lu- minescence intensity on the mole ratio of Yb^3＋ to Er^3＋ and Er^3＋ concentration were discussed in detail. When the mole ratio of Yb^3＋ to Er^3＋ is 25/1 and Er^3＋ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb^3＋ to Er^3＋ is 10/1 and Er^3＋ concentration is 0.15 %, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.     

Photoluminescence properties of ZnO thin films prepared by DC magnetron sputtering

ZnO thin films were prepared by direct current（DC） reactive magnetron sputtering under different oxygen partial pressures And then the samples were annealed in vacuum at 450 ℃. The effects of the oxygen partial pressures and the treatment of annealing in vacuum on the photoluminescence and the concentration of six intrinsic defects in ZnO thin films such as oxygen vacancy（Vo）, zinc vacancy（VZn）, antisite oxygen（OZn）, antisite zinc（Zno）, interstitial oxygen（Oi） and interstitial zinc（Zni） were studied. The results show that a green photoluminescence peak at 520 nm can be observed in all the samples, whose intensity increases with increasing oxygen partial pressure; for the sample annealed in vacuum, the intensity of the green peak increases as well. The green photoluminescence peak observed in ZnO may be attributed to zinc vacancy, which probably originates from transitions between electrons in the conduction band and zinc vacancy levels, or from transitions between electrons in zinc vacancy levels and up valence band.     

Photoluminescence and cathodoluminescence properties of CaLaGa3O7：Eu3＋ phosphors

The CaLaGa3O7:Eu3+ phosphor was prepared by a chemical co-precipitation method.Field emission scanning electron microscopy(FE-SEM),laser particle size analysis,X-ray diffraction(XRD),photoluminescence(PL),and cathodoluminescence(CL) spectra were util-ized to characterize the synthesized phosphor.The results revealed that the phosphor was composed of microspheres with a slight agglomer-ate phenomenon and was spherically shaped.The average grain size was about 1.0 μm.Eu3+ ions,as luminescent centers,substituted La3+ ions into the single crystal lattice of CaLaGa3O7 with the sites of Cs.Although the CL spectrum was greatly different from the PL spec-trum,it had the strongest red emission corresponding to the 5D0 →7F2 transition of Eu3+.Under the excitation of UV light(287 nm) and elec-tron beams(1.0-7.0 kV),the chromaticity coordinates of the phosphor were found to be in the nearly red and orange light regions,respec-tively.     

Single crystal β-Ga_2O_3: Cr grown by floating zone technique and its optical properties

β-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in β-Ga2O3 crystals Cr3 ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3 intrinsic emission was enhanced and the green lumines-cence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4T2 to 4A2. The studies manifest that the β-Ga2O3 crystals have the potential application for tunable laser.     

Single crystal β-Ga2O3: Cr grown by floating zone technique and its optical properties

β-Ga2O3 Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in -Ga2O3 crystals Cr3 ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3 intrinsic emission was enhanced and the green luminescence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4T2 to 4A2. The studies manifest that the β-Ga2O3 crystals have the potential application for tunable laser.     

Eu^3＋掺杂TiO2发光薄膜制备及其发光性能

为了寻找实用、廉价、性能良好的TiO2∶Eu3＋发光薄膜,采用溶胶-凝胶法制备了TiO2∶Eu3＋纳米发光薄膜.通过原子力显微镜与PL、PLE对样品薄膜的表面形貌和发光光谱进行了表征.研究结果表明：800℃退火的样品薄膜表面起伏不平,无开裂,且颗粒大小比较均匀,表面起伏度约为32nm,用540nm激发光源对800℃退火的TiO2∶Eu3＋发光薄膜进行激发时,样品显示出强红光发射,对应于Eu3＋的5 D0→7F2超灵敏跃迁;且荧光强度随着烧结温度的升高先增强再减弱,800℃时达到最大值,表明存在最佳的热处理温度.     

Crystallization and luminescence properties of Sm<Superscript>3+</Superscript>-doped SrO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> glass-ceramics

The Sm³⁺-doped SrO-Al₂O₃-SiO₂ (SAS) glass-ceramics with excellent luminescence properties were prepared by batch melting and heat treatment. The crystallization behavior and luminescent properties of the glass-ceramics were investigated by DTA, XRD, SEM and luminescence spectroscopy. The results indicate that the crystal phase precipitated in this system is monocelsian (SrAl₂Si₂O₈) and with the increase of nucleation/crystallization temperature, the crystallite increases from 66 % to 79 %. The Sm³⁺-doped SAS glass-ceramics emit green, orange and red lights centered at 565, 605, 650 and 715 nm under the excitation of 475 nm blue light which can be assigned to the ⁴G_5/2→⁶ H _j/2 (j=5, 7, 9, 11) transitions of Sm³⁺, respectively. Besides, by increasing the crystallization temperature or the concentration of Sm³⁺, the emission lights of the samples located at 565, 605 and 650 nm are intensified significantly. The present results demonstrate that the Sm³⁺-doped SAS glass-ceramics are promising luminescence materials for white LED devices by fine controlling and combining of these three green, orange and red lights in appropriate proportion.     

Sensitization and intra-molecular energy transfer of Eu<Superscript>3+</Superscript> by Tb<Superscript>3+</Superscript> in Eu-Tb binuclear complexes/PMMA

A series of Eu0.5Tb0.5(TTA)3Phen/PMMA (TTA=thenoyltrifluoroacetone,Phen=phenanthroline) and Eu0.5Tb0.5(TTA)3Dipy/PMMA (Dipy=2,2’-dipyridyl) were prepared by in-situ polymerization.The structures of the composites were characterized by IR spectra and electron spectrum.Photoluminescence properties were investigated by UV-Vis spectra and fluorescence spectra.Meanwhile,the energy transfer models were set up.The results indicated that polymer parts were attached with the rare-earth molecular parts in the composi...     

Frequency up-conversion luminescence properties and mechanism of Tm<Superscript>3+</Superscript>/Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped oxyfluorogermanate glasses

Oxyfluoride glasses were developed with composition 60GeO 2 ·10AlF 3 ·25BaF 2 ·(1.95-x)GdF 3 · 3YbF 3 ·0.05TmF 3 ·xErF 3 (x=0.02,0.05,0.08,0.11,0.14,0.17)in mole percent.Intense blue(476 nm),green(524 and 546 nm)and red(658 nm)emissions which identified from the 1G 4 →3H 6 transition of Tm3+and the(2H 11/2 ,4S 3/2 )→4I 15/2 ,4F 9/2 →4I 15/2 transitions of Er3+,respectively,were simultaneously observed under 980 nm excitation at room temperature.The results show that multicolor luminescence including white l...     

钨酸盐发光材料MWO_4:Eu~(3+)(M=Ca,Sr)的制备及表征

采用共沉淀法合成了CaWO4:Eu3+和SrWO4:Eu3+荧光粉体.利用荧光光谱仪测定了样品的光谱特性,结果表明,其主要激发波长为393nm和464nm,以393nm为激发波长说明样品能被近紫外光有效激发,并在614nm产生红色荧光;采用XRD分析其物相及晶体结构,发现生成的发光材料的晶型为四方晶系,晶粒均在纳米级,且在焙烧温度为400℃时生成的样品不含杂质,晶粒尺寸较小;扫描电镜显示400℃焙烧温度下生成的发光材料的样品颗粒大小在100~300nm之间,焙烧温度升高时,SrWO4:Eu3+的抗烧结能力弱,样品出现团聚,生成的样品颗粒变大.     

Interaction of rare earth ions in Sr<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>: Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> material

To discuss the function of Eu and Dy and their interaction in Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ long afterglow material, the Eu and Dy single doped and their co-doped Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ were prepared. The samples were characterized by X-ray diffraction (XRD), decay curves, photoluminescence (PL), and thermoluminescence (TL). The results indicate that Sr₂MgSi₂O₇: Eu has afterglow properties, and the doping of Eu ion in Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ can lower the depth of traps. Eu ion can not only serve as luminescence center, but also produce traps in the matrix, meanwhile, it also exerts certain influences on the traps produced by Dy in Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺. The Dy ion can not act as luminescence center but relates to the change of the traps in the Sr₂MgSi₂O₇ matrix.     

Phase transition and photoluminescence properties of Eu<Superscript>3+</Superscript>-doped ZnMoO<Subscript>4</Subscript> red phosphors

Eu³⁺-doped ZnMoO₄ with different doping concentrations were synthesized by a hydrothermal method. The effects of Eu³⁺ doping on the phase structure and photoluminescence (PL) properties of ZnMoO₄ were investigated. The result showed that the introduction of Eu3+ could lead to phase transition of ZnMoO₄. With the increase of Eu³⁺ doping amount, β-ZnMoO₄ was transformed to α phase gradually, which led to different photoluminescence performances. The optimized doping concentration of Eu³⁺ was 6 mol% for the highest emission intensity at 615 nm. Its CIE chromaticity coordinates were (0.667, 0.331), which were very close to the values of standard chromaticity (0.67, 0.33) for National Television Standards Committee (NTSC) system. Therefore, Eu³⁺-doped ZnMoO₄ is considered to be a promising red-emitting phosphor for white LED applications.     

机械力化学法合成ZnO:Eu3+,Li+及其荧光性能研究

采用机械力化学法与热分解相结合的方法制备了ZnO:Eu3+,Li+纳米粉末,用SEM、XRD、TG-DSC、UV-Vis、FL等检测手段对样品进行了表怔。结果表明：Eu3+和Li+成功掺入ZnO基质中;样品颗粒分布均匀,粒径为50nm,其发射主峰位于611nm处;其荧光性能与热处理温度及Eu,Li的掺杂比例密切相关。     

Combustion synthesis and luminescent properties of CaO: Eu<Superscript>3+</Superscript>, M<Superscript>+</Superscript> (M=Li,Na, K) phosphor

Li⁺, Na⁺, or K⁺ co-doped CaO: Eu³⁺ phosphors were prepared by the combustion synthesis method and characterized by X-ray diffraction (XRD), photoluminescence and photoluminescence excitation (PL-PLE) spectra. The experimental results show that, upon excitation with 250 nm xenon light, the emission spectrum of the CaO: Eu³⁺ consists of 4f-4f emission transitions from the ⁵ D ₀ excited level to the ⁷ F _J (J=1, 2, 3) levels with the mainly electric dipole transition ⁵ D ₀→⁷ F ₂ of Eu³⁺, indicating that the Eu³⁺ occupies a low symmetry. The charge-transfer band (CTB) shows somewhat red shift with the decreasing ionic radii of co-doped alkali metal ions. The PL and PLE intensities are significantly enhanced, especially the strongest intensity of luminescent is CaO: Eu³⁺, Li⁺ phosphor, when alkali metal ions are incorporated. The strongest peak of emission is slightly shifted from 614 to 593 nm, indicating that the Eu³⁺ ion locates in a symmetric position (O _h ) when alkali metal ions are incorporated.