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＋.     

Synthesis and optical properties of Dy~（3＋）, Li~＋ doped CaMoO_4 phosphor

A series of CaMoO4 phosphors doped with trivalent dysprosium ions (Dy3+) and lithium (Li+) were prepared by solid state method at 750 °C for 3 h. X-ray diffraction (XRD) confirmed the crystal structure and quality of phosphors. Scanning electron microscopy (SEM) in- dicated that the phosphors presented good crystalline state, and the crystalline grain sizes were about 0.5-3.0 μm. The emission spectra showed that the phosphors had intense emission at 480 (4F9/2→6H15/2), 576 (4F9/2→6H13/2) and 660 nm (4F9/2→6...     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Cathodoluminescent properties of Tb^3＋-doped yttria nanocrystallites

The Tb³⁺-doped Y₂O₃ nanopowders were synthesized using the modified Pechini method. The average size of nanocrystallites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr:Al₂O₃ was mixed with Tb³⁺:Y₂O₃ powders and its normalized emission was used to measure a relative intensity of Tb³⁺:Y₂O₃. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.     

Synthesis,structural and optical properties of SrZrO3：Eu3＋phosphor

Eu3+ activated Sr1–xEuxZrO3(x=0.01–0.04) phosphor with perovskite structure was successfully synthesized by using combustion method.The structure,morphology and optical properties of the material were characterized by X-ray diffraction,scanning electron microscopy and fluorescence spectrometry.The XRD results indicated that crystals of SrZrO3:Eu3+ belongs to tetragonal perovskite system.The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO3:Eu3+ due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant.Thus,the prepared phosphor showed remarkable luminescent properties which find applications in field emission display(FED) and plasma display panel(PDP) devices.     

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...     

Photoluminescence properties of LaF3：Eu^3＋ nanoparticles prepared by refluxing method

The europium-doped LaF3 nanoparticles were prepared by refluxing method in glycerol/water mixture and characterized with X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), UV-vis diffuse reflectance spectrum, and photoluminescence spectra. The results of XRD indicated that the obtained LaF3: Eu3+ nanoparticles were well crystallized with a hexagonal structure. The FE-SEM image illustrated that the LaF3: Eu3+ nanoparticles were spherical with an average size around 30 nm. Under irradiation of UV light, the emission spectrum of LaF3: Eu3+ nanoparticles exhibited the characteristic line emissions arising from the 5D0→7FJ (J=1, 2, 3, 4) transitions of the Eu3+ ions, with the dominating emission centered at 590 nm. In addition, the emissions from the 5D1 level could be clearly observed due to the low phonon energies (-350 cm-1) of LaF3 matrix. The optimum doping concentration for LaF3: Eu3+ nanoparticles was determined to be 20mol.%.     

Hydrothermal synthesis and luminescence properties of Eu3＋ and Sm3＋ codoped BiPO4

Eu3+/Sm3+codoped BiPO4 phosphors were synthesized via a facile hydrothermal method with surfactant-free environment. The X-ray diffraction analysis demonstrated that the samples possessed the standard BiPO4 monoclinic structure. Scanning electron microscopy images showed that all samples composed of well-dispersed, micrometer-sized crystals with shuttle-like shape. Energy transfer from Sm3+to Eu3+was confirmed by the luminescence spectra and the decay processes of Sm3+ 4G5/2 →6H5/2 emission. Orange-red luminescence could be obtained in Eu3+/Sm3+codoped BiPO4 phosphors. The average lifetime of Sm3+ 4G5/2 →6H5/2 emission decreased from 2.70 ms in BiPO4 :0.03Sm3+to 2.37 ms in BiPO4 :0.03Sm3+,0.05Eu3+. The strong and wide absorption band around 395 nm, originating from both7F0 →5L6 transition of Eu3+and6H5/2 →4K11/2 transition of Sm3+, endowed BiPO4 :Eu3+,Sm3+ phosphors with the potential application in the fields of near UV-excited white-light-emitting diodes.     

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.     

Luminescence properties and energy transfer of host sensitized CaMoO4：Tb^3＋ green phosphors

A series of CaMoO 4 :xTb 3+(x=0.01,0.03,0.05,0.07,0.09,0.15 and 0.20) phosphors in pure phase were prepared via high temperature solid-state reaction approach.The crystal structure of the phosphors was investigated by X-ray diffraction(XRD),and the optical properties were investigated by Fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) spectroscopy.The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping concentration of the activator Tb 3+ was 20 mol.%.The concentration quenching occurred at x=10 mol.%,from which the critical distance of activator was calculated to be about 1.14 nm.The CIE coordinates were estimated to be close to the standard green value.The host sensitized samples had potential application as green phosphors.     

Luminescent properties of Ba3Gd（BO3）3：Eu^3＋ phosphor for white LED applications

Luminescent material Ba3Gd(BO3)3 doped with Eu3+ ion was prepared by high temperature solid-state method. The preparing conditions, luminescent properties, and particle morphology of Ba3Gd(BO3)3:Eu3 + phosphor were studied with X-ray diffraction (XRD), fluorescence spectroscopy, and scanning electron microscopy (SEM). The results obtained by XRD showed that pure phase of Ba3Gd(BO3)3 was obtained at 1000℃. Images from SEM displayed that the particles of Ba3Gd(BO3)3:Eu3+ phosphor had a spherical shape with an average diameter of about 200-400 nm. The luminescence spectra showed that Ba3Gd(BO3)3:Eu3+ phosphor was effectively excited by the near ultraviolet (UV) light (396 nm) and blue light (466 nm). The main emission peaks of Ba3Gd(BO3)3:Eu3+ phosphor were assigned to the supersensitive transition 5D0-7F2 (611 and 616 nm) of Eu3+ ion when samples were excited at 255 and 396 nm, respectively, and the luminescent intensity of Ba3Gd(BO3)3:Eu3+ at 611 and 616 nm reached to the maximum when the doped content of Eu3+ ion was 10mol.%. Therefore, this phosphor could be a promising red component for possible applications in the field of white LED.     

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.     

Effect of Y3＋, Gd 3＋and La3＋dopant ions on structural,optical and electrical properties of o-mullite nanoparticles

Dielectric ceramics of M(x) Al6(1–x) Si2 O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffraction profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. TEM images showed regular orthorhombic crystal morphology for the pure mullite sample. Meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exothermic peak temperature of mullite was shifted to the lower value with M3+ion insertion. The photoluminescence spectra were studied for mullite samples, and it was found that the intensity of the emission spectra was affected by the M3+ion type. It was found that, Y3+doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region(1 MHz). Meanwhile, Gd3+ doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region(1 GHz).     

Influence of cooling rate and addition of lanthanum and cerium on formation of nanoporous copper by chemical dealloying of CUlsAIss alloy

The influence of cooling rate and addition of La and Ce on the formation of nanoporous copper by chemical dealloying of Cu15Al85 alloy was studied. The components and microstructures of nanoporous copper were characterized by utilizing X-ray diffrac-tion, field emission scanning electron microscopy and energy dispersive X-ray analysis. N2 adsorption/desorption experiments were used to evaluate specific surface areas of samples. The results showed that, with the increase of cooling rate, phase composition of precursor alloy almost had no change, the ligament size of nanoporous copper had a decrease trend, and specific surface area in-creased gradually. And it was found that the specific surface area of the nanoporous copper obtained by Cu15Al85 alloy containing La and Ce was 63.258 m2/g, which was more than 11.739 m2/g compared with the nanoporous copper dealloying by Cu15Al85 alloy without La and Ce under the same conditions.     

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.     

Upconversion emission of SrYbF5：Er3＋nanosheets modified by Tm3＋ions

Through a hydrothermal route, the Er3＋and Tm3＋co-doped SrYbF5 nanosheets were synthesized. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and luminescence spec-tra. Under the excitation of 980 nm laser irradiation, the upconversion emissions of Tm3＋ions centered at 474 nm （1G4→3H6）, 679 nm （3F2→3H6）, 699 nm （3F3→3H6）, 803 nm （3H4→3H6） and emissions of Er3＋ions centered at 522 nm （2H11/2→4I15/2）, 543 nm （4S3/2→4I15/2）, 654 nm （4F9/2→4I15/2） were observed. The upconversion emissions of Er3＋ions were adjusted by the concentration of Tm3＋ions. The energy transfer mechanisms among Er3＋-Yb3＋-Tm3＋in SrYbF5 nanosheets were discussed.     

Hydrothermal synthesis and luminescent properties of Li_xEu_xSr_（1-2x）MoO_4 red phosphor

LixEuxSr1-2xMoO4 red phosphors were synthesized via a facile hydrothermal method with various reaction time and ion contents of Eu3+ and Li+.As-synthesized samples were characterized by X-ray diffraction(XRD),thermogravimetry(TG),field emission scanning electron microscopy(FE-SEM) and fluorescence spectrophotometry.The XRD results revealed the formation of scheelite-like phosphor structures.The excitation spectra indicated the presence of two main excitation peaks located at 396 and 466 nm,suggesting that t...     

Photoluminescence properties of Sm3＋-doped LiY（Mo04）2 red phosphors

A series of novel Sm3＋-doped LiY（MoO4）2 red phosphors under the UV excitation were synthesized by solid state reaction at 800 ℃ for 7 h. The data measured by X-ray diffraction （XRD） indicated that the samples were all pure phases of LiY（MoO4）2. Their excitation spectra had a broad band ranging from 250 to 350 nm and several sharp peaks. The centers of the peaks were located at about 365 nm （6H5/2→4D3/2）, 378 nm （6H5/2→rp7/2）, 406 nm （6H5/2→4FT/2）, 420 nm （6H5/2→6ps/2）, 442 nm （6H5/2→4Gg/2）, 471 nm （6H5/2→4I13/2） and 482 nm （6H5/2→419/2）, respectively. The strongest emission was excited by 406 nm, and the main emissions were located at 568 nm （4G5/2→6Hs/2）, 610 nm （4Gs/2→rH7/2）, 649 nm （4G5/2→6H9/2） and 710 nm （4Gs/2→6HII/2）. Photoluminescence prop- erties were determined for various concentrations of Sm3＋-doped LiY（MoO4）2 host, and the luminescence intensity had the best value when x=0.02 in LiYix（MoO4）2：xSm3＋.     

Preparation and photocatalytic activity of La^3＋ and Eu^3＋ co-doped TiO2 nanoparticles： photo-assisted degradation of methylene blue

Rare earth ions La³⁺ and Eu³⁺ co-doped TiO₂ photocatalyst (La-Eu/TiO₂) was prepared by sol-gel method, and characterized by various techniques such as X-ray diffraction (XRD), specific surface area and porosity (BET and BJH), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the La-Eu/TiO₂ was evaluated by the degradation of methylene blue (MB) under UV light irradiation. The catalyst had a relatively uniform particle diameter distribution in the range of 40–60 nm. When calcining at 600°C, the XRD patterns of La-Eu/TiO₂ indicated the anatase phase, while the XPS patterns showed the Ti⁴⁺, La³⁺ and Eu³⁺ ions existence. The DRS spectra showed red shift in the band-gap transition. The experimental results of MB degradation demonstrated that the photocatalytic activity of La-Eu/TiO₂ was significantly enhanced due to better separation of photogenerated electron-hole pairs.     

Fabrication and characterization of YVO4：Eu^3＋ nanomaterials by the microwave technique

Fabrication and characterization of YVO4:Eu3+ nanophosphors prepared by microwave(MW) irradiation assisted soft template synthesis were reported.The effects of synthesis conditions such as different powers of MW irradiation,pH values and concentration of reac-tion materials on properties of nanophosphor were also investigated to obtain the controllable size,morphology and high luminescence effi-ciency.Morphology,crystalline structure,and optical properties were characterized by field emission scanning elect...