Luminescence Properties of Rare Earth Ions in Cadmium Metasilicate

The luminescence properties of CdSiO3:RE^3 phosphors doped with various rare earth ions are reported. The series of rare earth ions doped CdSiO3 phosphors are prepared by the conventional high-temperature solid-state method, and characterized by XRD and photoluminescence (PL) spectra. The results of XRD measurement indicate that the products fired under 1050 ~C for 3 h have a good crystallization without any detectable amount of impure phase. The PL spectra measurement results show that CdSiO3 is a novel self-activated luminescent matrix. When rare earth ions such as Y^3 ,La^3 , Gd^3 , Lu^3 , Ce^3 , Nd^3 , Ho^3 , Er^3 , Tm^3 and Yb^3 are introduced into the CdSiO3 host, one broadband centered at about 420 nm resulted from traps can be observed. In the case of other earth ions which show emissions at the visible spectrum region, such as Pr^3 , Sm^3 , Eu^3 , Tb^3 and Dy3 , the mixture of their characteristic line emissions with the ～420 nm strong broadband luminescence results in various emitting colors. As a consequence, different emitting colors can be attairied via introducing certain appropriate active ions into the CdSiO3 matrix. In additional, this kind of phosphors shows good long-lasting properties when excited by UV light. All the results show that CdSiO3 is a potential luminance matrix.     

Synthesis and luminescence properties of SrAleO4：Eue＋,Dy3＋ hollow microspheres via a solvothermal co-precipitation method

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process.The structure and particle morphology were investigated by X-ray diffraction(XRD),scanning and transmission electron microscopy(SEM and TEM)pictures,respectively.The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented.After being irradiated with ultraviolet(UV)light,the spherical phosphor emitted long-lasting green phosphorescence.Both the photoluminescence(PL)spectra and luminance decay,compared with that of commercial bulky powders,revealed that the phosphors had efficient luminescent and long lasting properties.It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.     

Reddish orange long lasting phosphorescence of Sm3+ in Sr2ZnSi2O7:Sm3+ phosphors

Long lasting phosphorescence phosphors with composition of (Sr1-xSmx)2ZnSi2O7 were prepared by conventional high-temperature solid-state method. Their properties were systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence spectra. The results showed that these phosphors emitted reddish orange light that corresponds to the characteristic emission due to the 4G5/2→6H5/2, 6H7/2 and 6H9/2 transitions of Sm3+. After the UV light excitation source was switched off, th...     

Luminescent properties of blue long-lasting phosphorescence phosphors Sr6Al18Si2O37：Eu2＋,RE3＋

A series of novel blue long-lasting phosphorescence phosphors Sr6A118Si2037：Eu^2＋,RE^3＋ （RE3＋=Ho^3＋, Gd^3＋, Dy^3＋ and Pr^3＋） were prepared by the conventional high-temperature solid-state reaction in a reductive atmosphere. Their properties were systemati- cally investigated utilizing X-ray diffraction （XRD）, photoluminescence, phosphorescence and thermoluminescence （TL） spectra. The phosphors emitted blue light that was related to the emission of E~＋ due to 5d-4f transition. Bright blue long-lasting phosphorescence （LLP） could be observed after the excitation source was switched off. For the optimized sample, the blue long-lasting phosphores- cence could last for nearly 4 h in the light perception of the dark-adapted human eye （0.32 mcd/m2）. The effects of RE3＋ ions on phosphorescence properties of the phosphors were studied, and the results showed that the co-doping of RE^3＋ ions greatly enhanced the intensity of the peak around 315 K which was related to the long lasting phosphorescence of the phosphors at room temperature and consequently improved the performance of the blue phosphorescence such as intensity and persistent time.     

Synthesis and spectral characteristics of La2MoO6：Ln3＋ （Ln=Eu, Sm, Dy, Pr, Tb） polycrystals

The novel phosphors of La 2 MoO 6 activated with the trivalent rare earth Ln 3+ (Ln=Eu, Sm, Dy, Pr, Tb) ions were synthesized by solid state reactions at high temperature in air atmosphere, and their phase impurities and luminescent properties were studied. The photoluminescence (PL) excitation and emission spectra, and decay curves were employed to study their luminescence properties. The lifetimes of the characteristic emissions from Ln 3+ ions were in the order of millisecond except Pr 3+ ions. (LaEu 1-x ) 2 MoO 6 was a promising phosphor for practical application and the optimum concentration was x=0.075. The concentration quenching mechanism of Eu 3+ was also discussed by theoretical fitting using Burshtein model.     

A white long-lasting phosphor Y2O2S:Tb3+, Sm3+: an improvement of Y2O2S:Tb3+

As an improvement of reported Y202S:Tb3 , a white-light long-lasting phosphor: Y2O2S:Tb3 , Sm3 was prepared by the solid-state reaction. The photo-luminescence spectra showed that the position and shape of Th3 and Sm3 emissions under UV excitation were similar in this host, which ensured a stable white emission color (daylight standard of IEC) under different excitations. The decay curves of co-doped samples indicated that the decay times of emissions of the two ions were close. The thermo-luminescence measurement suggested that the traps created by the doped Sm3 ions were helpful to postpone the white afterglow of co-doped samples. Therefore, thefunction of co-doped Sm3 ions was confirmned as improving the white emission colors of samples and acting as new trap centers.     

Preparation and characterization of flower-like SrAIeO4：Eu^2＋,Dy^3＋ phosphors by sol-gel process

A flower-like Eu²⁺ and Dy³⁺ co-doped SrAl₂O₄ long-lasting phosphorescent (LLP) phosphor was synthesized via the inorganic- salt-based sol-gel method. The crystal structure, morphology and optical properties of the composite were characterized. X-ray diffraction diffusion (XRD) data and DSC-TG curves of the phosphor revealed that the SrAl₂O₄ crystallites have been formed after the precursor was calcined at 900 °C and to be single-phase SrAl₂O₄ at 1100 °C. The SEM photographs indicated that the sample exhibited a universal flower-like morphology with crystallite size of about 1-2 μm. After being irradiated with ultraviolet (UV) light, the flower-like phosphor emitted long-lasting green phosphorescence with an excitation peak at 365 nm and emission peak at 500 nm which was ascribed to the characteristic 5d-4f transition of Eu²⁺. Both the PL spectra and the luminance decay curve revealed that this phosphor exhibited efficient luminescence and long lasting properties.     

A New Yellow Long Lasting Phosphor Y2O2S∶Ti

A new kind of doped rare earth free phosphor Y2O2S∶xTi(0＜x≤0.10) with doped Ti as activative center was synthesized by solid state reaction and sintered at 1200 ℃ for 2.5 h under reducing atmosphere. XRD patterns, photoluminescence spectra, time-resolved phosphorescence spectra and decay curves of the phosphor were investigated. XRD results reveal that a single Y2O2S phase exists with Ti content up to 6%(mol fraction). Yellow long lasting phosphorescence for present materials was observed in the dark with naked eye after the removal of the excitation light. From the time-resolved phosphorescence spectra the broad emission band centered at 565 nm was confirmed to be responsible for the long lasting phosphorescence which could maintain above 1 h. The possible mechanism responsible for the long lasting phosphorescence of the Y2O2S∶Ti phosphor was proposed.     

Sol-gel processed Ce^3＋, Tb^3＋ codoped white emitting phosphors in Sr2Al2SiO7

Sr2Al2SiO7：Ce^3＋, Tb^3＋ white emitting phosphors were fabricated using the sol-gel method. X-Ray Powder Diffraction （XRD） analysis confirmed the formation of Sr2Al2SiO7：Ce^3＋, Tb^3＋. Scanning Electron Microscopy （SEM） observation indicated that the microstructure of the phosphor consisted of regular fine grains with an average size of about 0.5-1 μm. Luminescence properties were analyzed by measuring the photoluminescence spectra. The Ce^3＋, Tb^3＋-codoped Sr2Al2SiO7 phosphors showed four main emission peaks： one at 414 nm for Ce^3＋ and three at 482, 543, and 588 nm for Tb^3＋. The emission spectra of the samples with different doping concentrations showed that the Tb^3＋ emission was dominant because of the persistent energy transfer from Ce^3＋. The decay characteristic was better than that prepared by the solid-state process in the comparable condition. The codoped phosphor displayed long persistent white phosphorescence.     

Luminescence and Energy Transfer Properties of Ca2Gd8(SiO4)6O2∶ A (A=Pb2+,Tm3+)Phosphors

Ca2Gd8(SiO4)6O2∶ A(A=Pb2 , Tm3 )phosphors were prepared through the sol-gel process. X-ray diffraction(XRD), scanning electron microscopy(SEM)and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 ℃. SEM study reveals that the average grain size is 300～1000 nm. In Ca2Gd8(SiO4)6O2∶ Tm3 phosphors, the Tm3 shows its characteristic blue emission at 456 nm(1D2-3F4)upon excitation into its 3H6 - 1D2(361 nm), with an optimum doping concentration of 1mol% of Gd3 in the host lattices. In Ca2Gd8(SiO4)6O2∶ Pb2 , Tm3 phosphors, excitation into the Pb2 at 266 nm(1S0-3P1)yields the emissions of Gd3 at 311 nm(6P-8S)and Tm3 at 367 nm(1D2 -3H6)and 456 nm(1D2-3F4), indicating that energy transfer processes of Pb2 - Gd3 and Pb2 - Tm3 have occurred in the host lattices.     

A single-phased white-emitting Ca_2Ga_2GeO_7:Dy~(3+) phosphor with different charge compensation ions

A novel white-emitting Ca_2Ga_2GeO_7:Dy~(3+) phosphor was synthesized via a high-temperature solid-state reaction.The crystal phase was analyzed by X-ray diffraction(XRD),and the photoluminescence(PL) properties were studied by luminescence spectra and fluorescence decay curves.Under the excitation of 347 nm,the obtained phosphor exhibited strong emission in the blue region peaked at 478 nm,yellow at 574 nm and a weak red emission band at 665 nm,corresponding to the characteristic transitions of ~4F_(9/2)to ~6H_(15/2),~6H_(13/2) and ~6H_(11/2) of Dy~(3+),respectively.By varying the doping concentration of Dy~(3+),tunable colors from blue-white to yellow-white were obtained in the phosphors.Besides,by codoping charge compensators(Li~+,Na~+,K~+ and Ga~(3+)) in Ca_2Ga_2GeO_7:Dy~(3+),the optimum CE color coordinate and PL intensity were obtained in Ca_2Ga_2GeO_7:Dy~(3+),K~+.Accordingly,the PL mechanism of Ca_2Ga_2GeO_7:Dy~(3+) was discussed briefly.     

Synthesis and characterization of needle-like BaAleO4：Eu,Dy phosphor via hydrothermal-homogeneous precipitation method

A needle-like Eu2+ and Dy3+ co-doped BaAl2O4 long-lasting phosphor was synthesized via a hydrothermal-homogeneous precipitation method assisted by cetyl trimethyl ammonium bromide(CTAB) as a template.The crystal structure,morphology and optical properties of the composites were characterized.XRD results showed that the single-phase BaAl2O4 was formed at 900 ℃ in an active carbon atmosphere,which was much lower than that prepared by traditional solid-state reaction method.Scanning electron microscopy(SEM) and transmission electron microscopy(TEM) observation revealed that the precursor had well-dispersed distribution and showed needle-like morphology with the average diameter of about 100 nm and the length up to 1 μm.The final product,BaAl2O4:Eu2+,Dy3+ phosphor,inherited the needle-like shape from precursor via adding the surfactant CTAB.After irradiation by ultraviolet radiation with 355 nm for 5 min,the phosphors emitted bluish green color long-lasting phosphorescence corresponding to the typical emission of Eu2+ ion.Both the photoluminescence spectra and luminance decay revealed that the phosphor had efficient luminescent and long-lasting properties.     

Synthesis of Long Afterglow Phosphors MAl2O4:Eu2+, Dy3+(M=Ca, Sr, Ba) by Microemulsion Method and Their Luminescent Properties

Long afterglow phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) were synthesized by microemulsion method, and their crystal structure and luminescent properties were compared and investigated. XRD patterns of samples indicate that phosphors CaAl2O4:Eu2 , Dy3 and SrAl2O4:Eu2 , Dy3 are with monoclinic crystal structure and phosphor BaAl2O4:Eu2 , Dy3 is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4:Eu2 , Dy3 (M=Ca,Sr,Ba) indicates that the luminescent materials can be excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) is found mainly at λem of 440 nm (M=Ca), 520 nm (M=Sr) and 496 nm (M=Ba) respectively, the corresponding colors of emission light are blue, green and cyna-green respectively. The afterglow decay tendency of phosphors can be summarized as three processes: initial rapid decay, intermediate transitional decay and very long slow decay. Afterglow decay curves coincide with formula I=At-n, and the sequence of afterglow intensity and time is Sr＞Ca＞Ba.     

Effects of Host Doping on Spectral and Long-Lasting Properties of Sm^3＋ -Doped Y2O2S

Gd- or Lu-doped long afterglow red phosphor Y2O2S：Sm^3＋ was synthesized using the high temperature flux fusion method. The obtained phosphors were analyzed using X-ray diffraction to determine the crystal structure, and the phase analyses show that the product is in single phase. The luminescence spectra and decay curve were measured on a Hitachi F-4500 fluorescence spectrophotometer. The decay time was determined on an ST-900PM weak light photometer. The analyses show that host doping of Lu improves both luminescence and decay time of the materials. The concentration of doped Lu and Sm was varied in order to determine the optimal condition and to synthesize the product with the best properties. The mechanism of the long afterglow was also briefly discussed.     

Luminescent properties and energy transfer of color-tunable Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors

Phosphors with controlled emission spectra are of great interest due to their application for white light emitting diodes.Herein, a new class of Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors were synthesized by a facile sol-gel combustion method. The phase structure,morphology, and luminescence properties of the phosphors were characterized by using powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and photoluminescence excitation and emission spectra,respectively. The results on luminescence properties indicated that co-doped Ce3＋ ions served as UV-light sensitizers with excitation energy partially transferred to Tb3＋ ions, leading to green emission from Tb3＋. Particularly, the corresponding emitting colors of the phosphors could be well-tuned from deep blue（0.16, 0.05） to green region（0.25, 0.45） by adjusting the molar ratio of Ce3＋/Tb3＋.     

Co-Precipitation Synthesis and Spectral Characteristics of Long Afterglow Phosphor Y2O2 S： Sm^3＋, Mg^2＋ , Ti^4＋

Y2O2S：Sm^3＋, Mg^2＋, Ti^4＋ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 ＋ molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 ＋ （4G5/2→6HJ ,J = 5/2, 7/2, 9/2）, and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 ＋ molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4＋ phosphor prepared by co-precipitation method was Sm^3＋ ions. The results indicated that the Y2O2S ： Sm^3＋ , Mg^2＋ , an efficient long afterglow phosphor.     

Effect of RE~(3+) electronegativities on luminescence property of Ba_5Si_8O_(21):Eu~(2+) persistent phosphor

A series of Ba_5Si_8O_(21):0.02Eu~(2+),0.09RE~(3+) persistent phosphors were synthesized by the solid-state reaction method.The measurement results of photoluminescence(PL),phosphorescence and thermoluminescence(TL)were analysed and discussed.The XRD results showed that samples codoped with different RE~(3+) were Ba_5Si_8O_(21) single pure phase.Under the excitation,all samples exhibited a broad Eu~(2+) characteristic emission,and the La~(3+) co-doped sample emitted the brightest photoluminescence even though its persistent luminescence property was the worst because of the weakest electronegativity.However,Nd~(3+) electronegativity was suitable,thus after activation,the Ba_5Si_8O_(21):Eu~(2+),Nd~(3+) sample had the best persistent luminescence performance with the highest phosphorescence intensity and the persistent luminescence decay time beyond 8 h.The Nd~(3+) co-doped sample also had the largest thermoluminescence integral area which proved effectively it had longer persistent luminescence time.The luminescence mechanism was also proposed to study the photoluminescence and persistent luminescence process.These results showed that RE~(3+) electronegativities were distinctly important for persistent phosphors and choosing suitable electronegativity codopant was conducive to enhancing the phosphorescent performance.     

Synthesis and Characterization of Rare Earth Complexes of Ferrocenylcarbonylhydrazine

Ｔｈｅｍｅｔａｌｃｏｍｐｌｅｘｅｓｏｆｈｙｄｒａｚｉｄｅｓｈａｖｅａｔｔｒａｃｔｅｄｃｏｎｓｉｄｅｒａｂｌｅｉｎｔｅｒｅｓｔｏｗｉｎｇｔｏｔｈｅｉｒａｎｔｉｆｕｎｇａｌａｎｄａｎｔｉｂａｃｔｅｒｉａｌａｃｔｉｖｉｔｉｅｓ[1 ,2 ] .Ｔｈｅｙｃａｎａｌｓｏｂｅｕｓｅｄａｓａｎａｌｙｔｉｃａｌｒｅａｇｅｎｔｓ[3 ]ａｎｄｅｘｔｒａｃｔｉｎｇａｇｅｎｔｓｆｏｒｍｅｔａｌｓａｌｔｓ[4 ] .Ｍａｎｙｃｏｍｐｌｅｘｅｓｏｆｈｙｄｒａｚｉｄｅｓｈａｖｅｂｅｅｎｓｙｎｔｈｅｓｉｚｅｄａｎｄｃｈａｒａｃｔｅｒｉｚｅｄ[5]…     

Effect of mixing process on the luminescent properties of SrAl_2O_4:Eu~(2+),Dy~(3+) long afterglow phosphors

A new mixing method was developed for solid-state reaction synthesis of SrAl2O4:Eu2+,Dy3+ long afterglow phosphors.The morphology and crystal structure of the phosphors were analyzed with scanning electron microscope(SEM) and X-ray diffractometer(XRD).The excitation and emission spectra of the long afterglow phosphors were measured,and the main emission band was around 514 nm.The decay time of the product was measured and compared with the phosphors prepared using dry-mixing method and wet-mixing method.It ...     

含N_2O_2四齿希夫碱配体的稀土有机配合物的合成和表征

室温下 ,采用 Schlenk操作技术 ,用 Cp3L n和对称的希夫碱双水杨醛缩邻苯二胺 ( H2 SAL OPHEN)为原料 ,物质的量之比为 1∶ 1,在四氢呋喃介质中反应 ,合成了六个新型配合物 Cp L n SAL OPHEN( L n=Y,Pr,Sm,Ho,Er,Tm)。所有这些配合物都经过了元素分析、IR和 Ms表征