Effects of Doping Trace Sm^3＋ and Gd^3＋ on Luminescent Character of Y2O2S：Eu^3＋

After trace Sm^3＋ ions and Gd^3＋ ions doping, the emission intensity of red phosphors Y2O2S： Eu^3 ＋ was enhanced and the voltage character （relation between emission intensity and excitation voltage） was improved while the other properties of physics and chemistry were not changed. The origins of enhancement and improvement are discussed. Probably the distortion and the defect of crystals are decreased by the substitution of Gd^3＋ for Y^3＋ instead of Eu^3＋ for Y^3＋ , and thus the Eu^3＋ crystal field is improved, and radiationless process and energy loss resulted from crystal defect are weakened, which leads to increased luminescence intensity and voltage character improvement. The overlapping fluorescent spectra of Y2O2S： Sm^3＋ emission and Y2O2S：Eu^3＋ excitation as well as Eu^3 ＋ excitation spectra transitions spectra lead to energy transfer from Sm^3 ＋ sensitization of Sm^3＋ ions fectively. containing Sm^3＋ excitation the possibility of resonance ions to Eu^3＋ ions, and the to Eu^3＋ ions is achieved effectively.     

Synthesis and Luminescence Properties of Gd2O3：Eu^3＋ Phosphors

Gd2O3: Eu^3 phosphors were prepared by urea homogeneous precipitation with different surfactant and sol-gel method. XRD patterns show that all the obtained samples are in cubic Gd2O3, and the results of FTIR and fluorescent spectra conformed that OP is a good surfactant for preparing the Gd2O3:Eu^3 phosphors. The SEM photographs show that the particles prepared by urea homogeneous precipitation method are all spherical and well-dispersed, and grain morphology can be controlled by different surfactant. XRD and SEM indicate that the particle sizes prepared by sol-gel method are in the range of 5-30 nm, and the grain sizes increase with increasing of heated temperatures. Luminescence spectra indicat that the main emission peaks of all samples are at 610 nm, the intensities are different from samples prepared with different surfactant and the luminescence intensities increase with increasing of annealed temperatures.     

Adjustable Luminescence of SrAl2O4：Eu^2＋ , Dy^3＋ Assembled in Zeolite

Capsulating guest into the nanometer yoids of zeolites is a effective way to form novel host-guest material. In our work, stoichiometric SrAl2O4: Eu^2 , Dy^3 sol guest was prepared by sol-gel method and assembled into the nanometer channels of zeolite ZSM-5 host through mechanical mixing, hydrothermal reaction and microwave heating reaction, respectively. After being reduced and diffused in a microwave muffle, the fluorescence spectra of the host-guest materials exhibit remarkable blue shifts in comparison of that of SrAl2O4 : Eu^2 , Dy^3 . Some interesting phenomena in the assembled hostguest materials are that the after-glow emission spectra exist two bands at about 400 nm and 517 nm and the relative strengths of these two bands can be adjusted by changing the assembly methods and the assembly concentration. These are attributed to the fact that the phosphor was capsulated into the voids of zeolite ZSM-5 and generated the quantum size effect and the host-guest effect.     

Study on Luminescence Properties and Crystal-Lattice Environment of Eu^2＋ in Sr4-xMgxSi3O8Cl4：Eu^2＋ Phosphor

According to the Van Uitert experimental equation, crystal-lattice environment of Eu^2 in the Sr4Si3O8C14 crystal was discussed. By adding Mg^2 to the host lattice, Sr4-xMgxSi3O8C14:Eu^2 was synthesized and the emission peak shifted from blue-green (488nm) to blue-violet (411nm) with the increase of amount of the magnesium which replaced the strontium. By analyzing the spectra of Sr4-xMgxSi3O8C14:Eu^2 the two Eu^2 emission centers were found because of the change of crystal-lattice environment in the host and the crystal structure was obtained by X-ray diffraction data.     

Luminescence of Eu^3 ＋ in LnAlO3 （Ln = Gd, Y） under UV and VUV Excitation

Single phases of LnAlO3 : Eu^3 ( Ln = Gd, Y ) were obtained by the process of evaporation of their nitric acid solution, and then pyrolysis of their nitrate salts. On monitoring by 613 nm emission, broad bands at around 270 and 170nm were observed in the excitation spectrum of Gd0.95Eu0.05AlO3. These peaks could be assigned to charge transfer (CT)transitions of Eu^3 -O^2- and Gd^3 -O^2- respectively. All the transitions observed in Gd0.95Eu0.05AlO3 are faithfully reproduced in the Y0.95Eu0.05AlO3, but with an exception of the ^8S7/2→^6I11/2 transition of Gd^3 . The 153 nm broad band could be the CT transition of Y^3 -O^2 - . Accordingly, the efficiency luminescence of (Gd, Y) BO3 : Eu^3 was explained as a result of CT transitions of Gd^3 -O^2- and Y^3 -O^2- under 147 nm excitation. Under VUV excitation, Gd0.95Eu0.05AlO3 exhibits a bright red luminescence with CIE chromaticity coordinates of (0.623, 0. 335) with a PL intensity of 30 of the commercial phosphor (Gd, Y) BO3 : Eu^3 (KX-504A). The PL spectrum of Y0.95Eu0.05AlO3 is similar to that of Gd0.95Eu0.05AlO3. Calculation of the color coordinates gives x = 0. 636, y = 0. 340 with a PL intensity of 50 of the (Gd, Y) BO3 : Eu^3 ( KX-504A) for Y0.95Eu0.05AlO3, and confirms that it has the appearance of pure spectral red, corresponding approximately to 608 nm. It can be concluded that LnAlO3:Eu^3 is a promising red VUV phosphor.     

Preparation and Luminescence Properties of the New Long Phosphorescent Phosphors Ba1-x Cax Al2O4 ： Eu^2＋ , Dy^3＋

New long phosphorescent phosphors Ba1-x CaxAl2O4:Eu^2 , Dy^3 with tunable color emission were prepared and studied. The emission spectra show that the tuning range of the color emission of the phosphors is between 498 and 440 nm, which is dependent on x, under the excitation of UV. The wavelength of the afterglow increases with the increasing of x until x equals 0.6. The XRD patterns show that the single phase limit in the phosphors is below x value of 0.4.The Thermolumineseence spectra were measured to investigate the traps created by the doping of Dy^3 .     

VUV Spectroscopy of GdPO4： Eu^3＋ and GdBO3： Eu^3＋

The emission and the excitation spectra of GdPO4 ： Eu^3＋ and GdBO3： Eu^3 ＋ prepared by solid state reaction method were investigated using the synchrotron radiation source of SUPERLUMI station of HASYLAB. The energy transfer between Gd^3＋ and Eu^3＋ was discussed with the probability of quantum cutting process. In the excitation spectra monitoring the red emission from Eu^3＋ , the distinct lines corresponding to the intraconfigurational 4f-4f transitions from Gd^3＋ were observed for both samples, indicating an efficient energy transfer from host Gd^3＋ ions to the doped Eu^3＋ ions. The efficient energy transfer is necessary for the quantum cutting process based on the two-step energy transfer from Gd^3＋ to Eu^3＋ . However, the overlapping of the lines corresponding to Gd^3＋ ：^8S7/2→^6GJ and the broad excitation band （180 - 270 nm） due to Eu^3＋- O^2- charge transfer states （CTS） around 200 nm cause excitation energy on ^6GJ levels to dissipate into CTS by direct energy transfer, unfavorable to the cross relaxation energy transfer between Gd^3＋ and Eu^3＋, thus unfavorable to the quantum cutting process. With the help of the general rules governing the energy positions of Eu^3＋-O^2- ：CTS, the suggestions concerning searching suitable oxide hosts for Gd^3＋-Eu^3＋ quantum cutting were made.     

Site Selective Spectroscopy of Suffactant－Assembled Y2O3：Eu Nanotubes

Y2O3:Eu nanotubes were synthesized by a surfactant assembly mechanism. Under ultraviolet-light excitation,the nanotubes present luminescence properties different from that of Y2O3:Eu nanoparticles. The peak position of the charge transfer band in excitation spectra varies with the monitoring emission peaks, while the emission spectra are dependent on the excitation wavelength. Laser selective spectroscopy was performed to distinguish the local symmetries of the Eu^3 ions in the nanotubes. The results of laser-selective excitation indicate that the emission centers near the surface of nanotube wails exhibit inhomogeneously broadened spectra without spectral structures while the two sites (site B and site C) inside the nanotube walls present resolved spectral structures. It is concluded by the number and peak positions of the spectral lines that the sites B and C possess different site symmetries.     

Long-Lasting Properties of Rare Earth-Doped Y2O2S Phosphors

The aim of this presentation is to report a new result of afterglow materials. The Y2O2S:Ln^3 (Ln = Sm, Tm)phosphors show bright reddish orange and orange-yellow colors when excited by UV or visible light. The main spectroscopic characterizations of Sm^3 and Tm^3 in yttrium oxysulfide and their long-lasting phosphorescence were measured and discussed in this presentation. Their long-lasting phosphorescence can be seen by the naked eyes clearly for about one hour in the dark room after the irradiation light sources were removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize these long-lasting phosphorescence phosphors. The results of XRD indicate that the products synthesized through the flux fusion method under 1050℃ for 6 h have a good crystallization without any detectable amount of impurity phase. Both the PL spectra and luminance decay results reveal that these phosphors have efficient luminescent and good long-lasting properties. We believe that the experimental data gathered in our present work will be useful in finding some new long-lasting phosphors with different colors.     

Synthesis and Luminescence Properties of Ba2 MgSi2 O7 :Eu2+ under UV Excitation

Eu2 activated pyrosilicate phosphor were prepared under a reducing atmosphere by solid-state reaction.The crystal structure of Ba2 MgSi2 O7: Eu2 was analyzed by XRD method.The excitation spectrum of Ba2MgSi2 O7; Eu2 is composed of two broad bands centered at about 310 nm and 395 nm respectively.In the emission spectra, the peak wavelength is at about 507 nm under 380 nm UV excitation.It was found that the introduction of Zn2 into Ba2MgSi2O7: Eu2 Can effectively increase its emission intensity without changing the position of emission peak.And the Eu2 and Ce3 codoped pyrosilicate phosphor is the efficient bluish green phosphor under the excitation of long UV light and its emission intensity is stronger than Eu2 doped pyrosilicate phosphor.     

Site Selective Spectroscopy of Surfactant-Assembled Y_2O_3∶Eu Nanotubes

Nanometermaterialshaveattractedagreatdealofattentioninthelastdecadebecauseoftheirgreatpo tentialfornanotechnologicalapplicationsandforun derstandingsomefundamentalconceptsabouttherolesofdimensionalityandsizein ,forexample ,optical ,electrical ,andmechanicalproperties[1,2 ] .Differentshapes ,suchasparticles ,films ,wires ,andtubes ,havebeenfabricatedwithvarioustechniques[3～ 6 ] .Inparticular ,thenanotubesusuallypresentnovelproper tiesassociatingwiththeirsmalldimensions ,highanisotropy ,andintr…     

Preparation and Luminescence Properties of Y2O3:Eu3+ Nanorods via Post Annealing Process

Yttrium oxide doped with europium has a great prospective for FED and PDP phosphor application. In present study, the precursor of yttrium oxide hydroxide nitrate nanorod, which was prepared via hydrothermal reaction route using PEG-6000 as template from the starting Y(NO3)3 and KOH reactant system, was used to prepare Y2O3:Eu3 nanorod via a post annealing process during which the precursor with adjustable shape and size was transformed to final Y2O3:Eu3 product. XRD, field emission scanning electron microscopy (FE-SEM) and photoluminescence spectra (PL) were used to characterize the crystalline, morphology and luminescence properties of as-formed Y2O3:Eu3 products synthesized at different post annealing temperatures, respectively. The results indicate that grain morphology of obtained Y2O3:Eu3 product was nanorod with a mean diameter of about 40～60 nm and length of about 500～700 nm, the nanorod structure and morphology of obtained Y2O3:Eu3 product maintained during post annealing process and the size varied slightly with different annealing temperatures. Pure cubic Y2O3:Eu3 phase was formed and the size was the smallest at annealing treatment of 500 ℃. Under the annealing temperature below 500 ℃ its diameter increased with increasing annealing temperature, and remained in a stable size when the annealing temperature was above 500 ℃. The PL spectra of excitation spectra of Y2O3:Eu3 product show that it exhibits excitation band located at about 395 and 468 nm, respectively. Above two excitation bands could be ascribed to the transition 4f-4f of Eu3 ions in the Y2O3 host. On the other hand, the main emission peaks of the as-prepared products could be ascribed to the Eu3 ions transition from 5D0 to 7F2. Furthermore, the luminescent intensity was improved about three times when the annealing temperature increased from 500 to 1000 ℃.     

Research of Luminescence Properties on MO-RE2 O3 -B2 O3:Eu, Mn(M=Mg, Ca, Sr; RE=Y, La, Gd)

A series of phosphor of MO-RE2 O3-B2 O3: Eu, Mn ( M = Mg, Ca, Sr; RE = Y, La, Gd) were prepared and studied.Excitation spectra exhibited high absorption in UV region (370 ～ 400 nm).There existed two valence states for europium ions Eu2 and Eu 3 , the broad emission band peaking at 515 nm correspond to the 5d-4f emission transition of Eu2 , the sharp emission peaking at 590 and 610 nm correspond to the 5D0→7FJ(J = 1,2,3,4) emission transition of Eu 3 By the introduction of Mg and Y into MO-RE2O3-B2O3: Eu, blue-green emission was restrained ultimately and red emission peaking at 610 nm was enhanced strongly, intensity and colorimetric purity of red light were both enhanced.Furthermore, Mg1-xSrxO-Y2O3-B2O3: Eu was also researched, the introduction of Sr into MgO-Y2O3-B2O3:Eu gives rise to a shift to longer wavelengths of the position of the excitation peak, and the emission spectra varies with the increasing of x simultaneously.     

Study on Luminescence Properties and Crystal-Lattice Environment of Eu~(2 ) in Sr_(4-x)Mg_x Si_3O_8Cl_4∶Eu~(2 ) Phosphor

ChlorosilicatecrystalmaterialM4 Si3O8Cl4 (M =Ba ,Sr ,Ca)isasuitablehostlatticeforluminescencematerials .Adivalenteuropiumactivatedstrontiumchlorosilicatephosphorisakindofgoodblue greenemissionphotoluminescencematerialunderUVexcita tion .Itsluminescencepropertiesandcrystalstructurehavebeenintensivelystudied[1～4 ] .Inthechlorosili catehost ,theluminescenceofEu2 consistsofa4f6 5d1- 4f7(8S7/2 )broad bandemission ,whichbe longstoelectric dipoleallowedtransitionandhasthepropertiesoflargeabso…     

Cooperative energy transfer in Eu3+,Yb3+ codoped Y2O3 phosphor

Under 980 nm laser excitation,red emission(5D0-7FJ(J=0,1,2)) of Eu3+ was observed in cubic Y2O3 codoped with Eu3+ and Yb3+.The dependence of the upconverted emission on doping concentration and laser power was studied.Yb3+ emission around 1000 nm(2F5/2-2F7/2) was reported upon excitation of Eu3+ ions.The decay curves of 5DJ(J=0,2) emission of Eu3+ under excitation of 266 nm pulse laser were examined to investigate the Eu3+→Yb3+ energy transfer process.Cooperative energy transfer process was discussed as the possible mechanism for the visible up-conversion luminescence of Eu3+ and near-infrared down-conversion emission of Yb3+.     

Preparation,Structural Analysis and Luminescence Properties of Nanocrystalline Phosphor Gd2O3∶Eu

Nanocrystalline monoclinic and cubic Gd2O3∶Eu with different Eu3 concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd2O3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu3 (5D0→7F2) locates at 624 nm in monoclinic Gd2O3∶Eu and 611 nm in cubic sample. In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state(CTS) and f-f transitions of Gd3 and Eu3 were observed and discussed. The quenching concentration of monoclinic and cubic Gd2O3∶Eu is 10% and 15%, respectively, both of which are much higher than that of bulk Gd2O3∶Eu.     

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.     

Characterization of Y2O2S:Eu3+, Mg2+, Ti4+ Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y2O2S∶Eu3 , Mg2 , Ti4 was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S∶Eu3 x(0.01≤x≤0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S∶ Eu3 crystal structure, Eu3 ions only replaced Y3 ions′ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm (5D1→7F2 transition) to 626 nm (5D0→7F2 transition), and the maximum intensity was obtained when x=0.09 in Y2O2S∶Eu3 x(0.01≤x≤0.10). This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg2 or Ti4 ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg2 and Ti4 ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd*m-2). Thus the LLP mechanism was analyzed.