Synthesis of ordered mesoporous γ-Al_2O_3:Eu~(3+) with high luminous performance and thermal stability

An efficient and convenient one-step process was developed for synthesizing new effective red luminous materials through ordered mesoporous γ-alumina assembling with Eu3+. Employing P123 as a structure-directing agent and hydrochloric acid, citric acid as pH adjustor, ordered mesoporous γ-alumina was fabricated by simple sol-gel method. The pore structure was characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms and transmission electron microscopy (TEM). The as-synthesized γ-aluminas...     

Hydrothermal Preparation and Luminescence of LaF3：Eu^3＋ Nanoparticle

Pure andEu^3＋-doped LaF3 nanoparticle were prepared by a hydrothermal process at a low temperature and characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and fluorescence spectra. Well-dispersed nanopartiele with an average size of 30 nm and a hexagonal shape were synthesized. The effects of temperature and reaction time on the preparation of nanoparticle were investigated, and the growth mechanism of nanoparticle was briefly discussed. The effects of Eu^3＋-doped concentration, the calcination time and temperature were also investigated. An optimal Eu^3 ＋-doped concentration of 5% is found. Calcination temperature and prolonged of the nanoparticle at high time greatly reduce the fluorescence intensity. The sample calcinated at 600 ℃ for 6 h emits the strongest fluorescence.     

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.     

Synthesis and Luminescence of SrZnO2：Eu^3＋, Li^＋ Phosphor by Long Wavelength UV Excitation

SrZnO2 ： Eu^3 ＋ , Li^＋ phosphor powder by long wavelength UV excitation was synthesized by conventional solid-state reaction method. XRD and PL were employed to characterize their properties. The resuits show that Eu^3＋ ions preferentially occupy Sr^2＋ asymmetry cationic sites, thus emitting 612 nm red light originated from ^5D0 to ^7F2 transition. The luminescent intensity can be greatly enhanced with incorporation of Li^＋ ions. The excitation efficiency in range of 350 - 400 nm also increases greatly due to incorporating Li ^＋ ions. SrZnO2 ： Eu^3 ＋ , Li^＋ is a promising redemitting phosphor by long wavelength UV excitation.     

Sol-Gel Synthesis and Luminescent Characteristic of Doped Eu^3 ＋ Silicate-Silica Phosphor

Silicagelphosphorsdopedrareearthionshave attractedgreatattentionofmanyresearchersdueto theseadvantages,suchashighersamplehomogeneity,purityandstable,efficientandenvironmentallyfriend lyphotoluminescencematrixmaterials,whichisless toxicleadtonetconversione…     

Citrate-Gel Synthesis and Luminescent Properties of α-Zn3 （PO4）2 Doped with Eu^3＋

By using inorganic salts as raw materials and citric acid as complexing agent, α-Zn3(PO4)2 and Eu^3 doped α-Zn3( PO4)2 phosphor powders were prepared by a citrate-gel process. X-ray diffraction (XRD), TG - DTA, FF - IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500℃ and pure α-Zn3(PO4)2 phase is obtained at 800℃. And the results of XRD reveal that Eu^3 exists as EuPO4 in the powder. In the phosphor powders, the Eu^3 shows its characteristic red-orange(592 nm, ^5D0 -^7F1) emission and has no quenching concentration.     

Effect of TSL and PSL in Al^3＋-Doped BaFBr：Eu^2＋ at Difference Synthesis Conditions

Thermal stimulated luminescence (TSL) and photostimulated luminescence (PSL) were used to investigate the luminescent performance of Al^3 -doped BaFBr:Eu^2 in different synthetic conditions. Theory analysis shows that the decay of TSL spectra is different from that of PSL spectra. Theoretical calculation was used to investigate the effects of energy state in Al^3 -doped BaFBr:Eu^2 by different synthetic conditions. The relationship of color center‘s energy and different synthetic conditions is discussed.     

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.     

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.     

Hydrothermal preparation and persistence characteristics of nanosized phosphor SrS：Eu^2＋,Dy^3＋

Nanosized long-persistent phosphors SrS: Eu2+, Dy3+ were prepared by the hydrothermal method. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, and charge-coupled device spectrometry. The persistence characteristic was studied using the decay curves. The results showed that the emission intensity decreased sharply with temperature increasing, although the particle size increased. The S2- vacancies caused by oxidization served as shallow traps, and Dy3+ served as deep traps in SrS: Eu2+, Dy3+. The afterglow intensity of SrS: Eu2+, Dy3+ was higher than that of SrS: Eu2+ prepared at the same temperature. However, the minimization span of initial afterglow with temperature for the former sample was larger than that for the latter. Binary-doped phosphor decayed more slowly than the singly doped one. The afterglow of SrS: Eu2+, Dy3+ decayed more quickly with the increase of sintering temperature.     

Eu^2＋ Luminescence in BaZnAl10O17 ： Eu Phosphor

Eu^2 -doped BaZnAl10O17 phosphor was successfully obtained by coprecipitation method, in which oxalic acid and ammonia were used as precipitants, and precipitates were calcined at 1400 ℃ for 3 h. Its luminescent intensity was much stronger than the one obtained by solid-state reaction at high temperature. According to XRD, the crystal was identified as BaZnAl10O17 with β-Al2O3 structure.     

Sol-Gel Preparation and Luminescence Properties of BaMgAl10O17 ： Eu^2＋ Phosphors

The synthesis of BaMgAl10O17： Eu^2＋ （BAM） phosphors using the sol-gel method and their luminescence properties were reported. The blue-light emitting BAM was synthesized using citric acid and ethylene glycol as chelating materials. Emission of blue-light was obtained from these phosphors. The luminescent intensity increases as the temperature of heat treatment is increased, This study investigated the effects of the molar ratio of ethylene glycol to citric acid （Ф value）, with respect to the phase formation and luminescence properties of BAM. The variation of the Фvalue resulted in the change of the sol-gel reaction mechanism and the microstructures of the resultant powders. An increase in Фvalue leads to an increase in the rate of BAM phase formation. The photoluminescent intensity of the prepared phosphors increases with heating temperatures because of enhanced crystallization.     

Synthesis of Long Afterglow Phosphors MAI204：Eu^2＋ , Dy^3＋ （M=Ca, Sr, Ba） by Microemulsion Method and Their Luminescent Properties

Long afterglow phosphors MAl2O4：Eu^2＋ , Dy^3＋ （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：Eu^2＋, Dy^3＋ and SrAl2O4 ： Eu^2＋, Dy^3＋ are with monoelinie crystal structure and phosphor BaAl2O4：Eu^2＋ , Dy^3＋ is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4： Eu^2 ＋ , Dy^3＋ （M = Ca,Sr, Ba） indicates that the luminescent materials can he excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4：Eu^2＋ , Dy^3＋ （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 eyna-green respectively. The afterglow decay tendency of phosphors can he 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.     

Hydrothermal synthesis of SrF2：yb^3＋/Er^3＋ micro-/nanocrystals with multiform morphologies and upconversion properties

Micro-and nanocrystals cubic-phase SrF2:Yb3+/Er3+ upconversion luminescence phosphors were synthesized via a facile hydro-thermal route in the presence of different surfactants.The samples were characterized with X-ray diffraction (XRD),Fourier transform infra-red spectra (FT-IR),scanning electron microscopy (SEM),transmission electron microscopy (TEM),and upconversion emission spectra.As-prepared products showed a variety of morphologies,such as cubic-shaped microcrystal,hierarchical structure microspheres...     

Photoluminescent properties of LaF3：Eu^3＋ and GdF3：Eu^3＋ nanoparticles prepared by co-precipitation method

LaF₃:Eu³⁺ and GdF₃:Eu³⁺ nanoparticles were prepared by a co-precipitation method in the presence of the chelating agent, citric acid. The structural properties of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average crystallite size was estimated from the full-width at half-maximum (FWHM) of the diffraction peaks by the Scherrer equation. The sizes of the nanoparticles were 12 nm for LaF₃:Eu³⁺ and 17 nm for GdF₃:Eu³⁺. The luminescent properties of the nanoparticles were investigated by excitation and emission spectra. Energy transfer from Gd³⁺ to Eu³⁺ was observed.     

Synthesis and luminescence properties of CeF3：Tb3＋ nanodisks via ultrasound assisted ionic liquid method

CeF3 and CeF3：Tb3＋ nanocrystals were successfully synthesized by the ultrasound assisted ionic liquid （IL） method at room temperature. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, selected area electron diffraction （SAED）, high-resolution transmission electron micrographs （HRTEM） and photoluminescence （PL） spectra were employed to characterize the nanocrystals. The results of XRD indicated that the obtained samples crystallized well with a hexagonal phase crystal structure. SEM and TEM images demonstrated that the obtained CeF3：Tb3＋ nanocrystals had a discoid shapein the presence of ultrasound and IL, whereas only granular nanoparticles were obtained by magnetic stirring. The possible formation mechanisms of the crystal growth were proposed. The PL spectra of the CeF3：Tb3＋ nanodisks exhibited a strong green emission when excited at 254 nm. Furthermore, the photoluminescence intensity of CeF3：Tb3＋ of the discoid particles was largely improved com-pared with that of the granular nanoparticles.     

Luminescence properties of Eu2＋ -doped Ba3Si6O12N2 green phosphor： concentration quenching and thermal stability

The efficient Eu2+ -doped Ba3 Si6O12N2 green phosphors were prepared by a traditional solid state reaction method under N2 /H2 atmosphere at a temperature up to 1350 oC for 12h. Photoluminescence (PL) properties showed a broad emission band with a peak of 525 nm and the full width of half-emission maximums (FWHM) of 70 nm under 460 nm light irradiation. The X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) images of the synthesized powder demonstrated its pure phase and excellent crystallization. Quenching concentration in this phosphor was found to be 0.3. The mechanisms of concentration quenching and redshift of emission peak with increasing concentration of Eu2+ were studied. The temperature dependence measurement of this green phosphor revealed excellent thermal quenching property compared to silicate green phosphor. It is believed that Ba3 Si6O12N2 :Eu2+ is an excellent green phosphor for UV or blue chip based white LEDs.     

Synthesis of Long Afterglow Photoluminescent Materials Sr2MgSi2O7：Eu^2＋,Dy^3＋ by Sol-Gel Method

Long afterglow photoluminescent materials Sr2MgSi2O7 dopeo With Eu^2 ,Dy^3 were prepared by sol-gel method. The synthesized samples were characterized by X-ray diffraction. The excitation spectrum, emission spectrum and long decay curve were measured and analyzed. XRD pattern indicates that phosphor is with Sr2MgSi2O7 crystal structure. The wide range of excitation wavelength indicates that luminescent material can be excited by light from ultraviolet ray to visible light. The main peak of emission spectrum is located at 466nm. Sample excited by visible light can emit bright blue light, and the afterglow time lasts more than 8h.     

Thermal Stability and Luminescence Properties of Eu^3＋ and Tb^3＋ Complexes with a Silica Matrix by Sol-Gel Method

Ternary complexes of europium and terbium with benzoic acid and 1, 10-phenanthroline [RE(BA)3phen] (BA=benzoate phen=1,10-phenanthroline) were introduced into a silica matrix by sol-gel method. The thermal stability and luminescence behavior of the complexes in silica gels were studied in comparison with the corresponding solid-state complexes by thermal decomposition, excitation and emission spectra. The thermal stability of the complexes is enhanced in silica gel matrix and the luminescence remaines unchanged.