A white long-lasting phosphor Y_2O_2S:Tb^(3+), Sm^(3+): an improvement of Y_2O_2S:Tb^(3+)

As an improvement of reported Y2O2S：Tb^3＋, a white-light long-lasting phosphor： Y2O2S：Tb^3＋, Sm^3＋ was prepared by the solid-state reaction. The photo-luminescence spectra showed that the position and shape of Tb^3＋ and Sm^3＋ 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 Sm^3＋ ions were helpful to postpone the white afterglow of co-doped samples. Therefore, the function of co-doped Sm^3＋ ions was confirmed as improving the white emission colors of samples and acting as new trap centers.

A Novel White Light Emitting Long-lasting Phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 nm (4F9/26H13/2) and 486 nm (4F9/26H15/2), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 nm excitation. It indicated that this phosphor is a promising new luminescent material for practice application.

Photo-luminescence properties and thermo-luminescence curve analysis of a new white long-lasting phosphor: Ca_2MgSi_2O_7:Dy^(3+)

A white long-lasting phosphor Ca2MgSi2O7:Dy3+ was prepared by the solid-state reaction. A strong band peaked at 260 nm was shown in the excitation spectrum of 578 nm emission, which might be attributed to the oxygen deficiency of the host. After irradiated with 254 nm for 4 min, the white afterglow of the sample could be seen for 3 h. Moreover, the depths and frequency factors of trap centers were calculated from the thermo-luminescence curve of the sample, which indicated that the trap centers corresponding to the 414 K band were more helpful to the long-lasting phosphorescence.

Synthesis and Luminescence Properties of Red Phosphors:Mn^(2+) Doped MgSiO_3 and Mg_2SiO_4 Prepared by Sol-Gel Method

Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.

Templating Synthesis and Luminescent Properties of SrAl_2O_4∶Eu, Dy Phosphor Derived from A Mesoporous Precursor

Long-lasting SrAl2O4∶Eu, Dy phosphor was successfully prepared from a mesoporous precursor. The precursor was synthesized by templating method using nonionic Polyethylene Oxide (PEO) as surfactants, which was proved by TG-DTG, X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The analysis results indicated that regular cylindrical-to-hexagonal shaped pores with several nanometers were obtained. The structure and morphology of the SrAl2O4∶Eu, Dy phosphor by templating method was characterized by XRD and Scanning Electron Microscopy (SEM). The XRD results showed that a pure SrAl2O4 phase formed at 900 ℃ by templating method. The SEM morphologies of the obtained phosphors prepared by templating synthesis were uniform and porous multicrystalline with average diameter size of 5 μm. The broad-band UV-excited SrAl2O4∶Eu, Dy phosphor derived from a mosoporous precursor was observed at λmax=515 nm due to the transitions from the 4f65d1 to the 4f7 configurations of Eu2+ ion. The main excitation and emission intensity of the phosphor with this method were stronger than that obtained by solid state reaction method. And the obtained long-lasting phosphor with this method revealed a better afterglow compared to the phosphor prepared through solid state reaction method.

Efficient blue-light-excitable copper(Ⅰ) coordination network phosphors for high-performance white LEDs

The blue-light-excitable phosphors play a crucial role in the high-performance white LEDs. Here, we report on two new Cu(Ⅰ) coordination network materials as yellow-emitting phosphors prepared by suitably expanded π-conjugated triazole ligands. Upon blue-light irradiation, these complexes exhibit efficient solid-state emission and enhanced photostability. Through incorporating the yellow phosphor and a commercial blue-green powder(BaSi_(2)N_(2)O_(2):Eu^(2+)) with a blue LED chip, the phosphor-converted LED devices display remarkable white emission properties. The experimental results demonstrate that the Cu(Ⅰ)coordination network materials function as promising blue-light excitable phosphors with great application potential for full-spectrum white LEDs.

Study on white-light emission and light-emitting mechanism of hydrothermally synthesized YVO_4:1 mol.%Dy^(3+),x mol.%Eu^(3+) phosphor powders

White light-emitting YVO4:1 mol.%Dy3+,x mol.%Eu3+ phosphor powders with order morphology and well crystallization were hydrothermally synthesized at 180°C. The microstructure, white-light emission, and light-emitting mechanism of the powders were carefully studied using X-ray diffractometry, scanning electron microscopy and photoluminescence spectra. The excitation and emission spectra of the phosphor powders indicated the coexistence of efficient energy transfer from Eu3+ to Dy3+ and inefficient en-ergy transfer from Dy3+ to Eu3+ besides the energy transfer from VO43– to Eu3+. Increasing the Eu3+ concentration initially enhanced and then weakened the luminescent intensity of Dy3+. The white-light emissions of YVO4:1 mol.%Dy3+,xmol.%Eu3+ phosphor pow-ders were both related to the energy transfer between VO43– and Dy3+/Eu3+, as well as between Eu3+ and Dy3+. The inefficient energy transfer from Dy3+ to Eu3+ was first found.

Luminescence and Energy Transfer of Eu^2＋, Mn^2＋ in SrZnP2O7

The SrZnP2OT：Eu^2＋, Mn^2＋ phosphor is synthesized by high temperature solid state reaction. The luminescence properties and the energy transfer between Eu^2＋ and Mn^2＋ are investigated. The emission bands of this phosphor peaked at 42Ohm and 67Ohm are originated from the 5d → 4f transition of Eu^2＋ and from the 4T1 （4G） --〉 6A1 （6S） transit/on of Mn^2＋, respectively. With the increasing Mn^2＋ concentration, the intensity of fixed concentra- tion Eu^2＋ decreases and the intensity of Mn^2＋ also increases. It is suggested that there is an energy transfer from Eu^2＋ to Mn^2＋ in SrZnP2O7 host. According to Dexter＇s energy transfer formula of multipolar interaction, the energy transfer between Eu^2＋ and Mn^2＋ is due to the electric dipole-quadrupole interaction of the resonance transfer.

A novel Li^(+)-doped MgLuGaO_(4)phosphor with stable white-light emission and long persistent luminescence

In recent years,white persistent luminescence materials have received extensive attention due to the potential application of white light in the field of plant growth lighting.The white persistent luminescence materials synthesized by traditional methods either have strict requirements on the concentration of doped ions or cannot produce white light continuously and stably due to different decay rates of various emission centers,which limits their further application.In our work,we successfully synthesized a novel Li^(+)-doped MgLuGaO_(4)phosphor with stable white-light emission and long persistent luminescence.The broadband emission of MgLuGaO_(4):Li^(+)is mainly located at 350-650 nm,which has no change at different decay time,showing stable white-light emission.The persistent luminescence intensity is increased by 3.8 times and the persistent luminescence time is extended from 24 h to more than 36 h by doping Li+ions.Stable white-light and long persistent luminescence emission make it promising to be used in plant growth lighting.

Synthesis and luminescence properties of KCaPO_4:Eu^(2+),Tb^(3+),Mn^(2+) for white-light-emitting diodes(WLED)

In order to obtain a single-host white-light phosphor, a series of KCaPO4 powder samples tri-doped with Eu2＋, Tb3＋ and Mn2＋ were synthesized via high-temperature solid-state reaction method. Their structural and luminescence properties were investigated. Under proper ultraviolet excitation （255-405 urn）, white light was obtained, consisting of blue, green and red emissions stemming from Eu2＋, Th3＋, Mn2＋ ions respectively. The temperature stability of our sample was analyzed by studying the variation tendeney of CIE chromaticity coordinates at different temperatures. The results indicated that this phosphor could yield good color stability when utilized in WLED.

Effect of different RE dopants on phosphorescence properties of Sr_2Al_2SiO_7:Eu^(2+) phosphors

Different rare earth （RE） ions dopants were added into the SrAl2SiO7：Eu^2＋ phosphors in order to enhance the phosphorescence properties, and the effect of the RE ions including Yb^3＋, Ce^3＋, Nd^3＋, Dy^3＋ and Tm^3＋, was comparatively investigated. It was found that Nd^3＋ addition improved the phosphorescence properties obviously among all the studied RE ions. Therefore, Sr1.96-xAl2SiO7：xEu^2＋,yNd^3＋ phosphors were studied in detail, and the optimum Eu^2＋ and Nd^3＋ concentrations were determined with the afterglow time of about 20 min. The phase structures, photoluminescence （PL） properties, long-lasting phosphorescence （LLP） properties, afterglow decay curves and thermo-luminescence （TL） for the selected phosphors during the corresponding study were investigated. All the phosphors exhibited green PL emission and LLP emission. There were two TL bands located at about 325 and 380 K for the studied samples, and the relationship between RE addition and phosphorescence properties was dis- cussed.

Synthesis and characterization of needle-like BaAl_2O_4:Eu,Dy phosphor via hydrothermal-homogeneous precipitation method

A needle-like Eu2＋ and Dy3＋ co-doped BaAI204 long-lasting phosphor was synthesized via a hydrothermal-homogeneous pre- cipitation method assisted by cetyl trimethyl ammonium bromide （CTAB） as a template. The crystal structure, morphology and opti- cal properties of the composites were characterized. XRD results showed that the single-phase BaA1204 was formed at 900 ℃ in an active carbon atmosphere, which was much lower than that prepared by traditional solid-state reaction method. Scanning electron mi- croscopy （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, BaAI2Oa：Eu〉,Dy3＋ phosphor, inherited the needle-like shape from precursor via adding the surfactant CTAB. After irradiation by ul- traviolet radiation with 355 nm for 5 rain, 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 lumi- nescent and long-lasting properties.

Template-free Fabrication and Luminescent Characterization of Highly Uniform and Monodisperse Y_2O_2S:Sm^(3+) Hollow Submicrospheres

Well dispersed and homogeneous Y2O2S：Sm3＋ hollow submicrospheres were successfully achieved by a template- free solvothermal method combining with a postcalcining process. The crystalstructure and particle morphology were investigated by the X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectra, scanning and transmission electron microscopy （SEM and TEM）, respectively. A possible growth mechanism was proposed to reveal the formation process. Luminescence properties of the Y202S：Sm3＋ long-lasting phosphor were an- alyzed by measuring the excitation spectra, emission spectra, afterglow decay curve and thermoluminescence curve. The excitation spectra indicated that the phosphor could be excited effectively by the ultraviolet-light emitting diode （UV-LED） or blue LED, and the emission spectra showed that the phosphor could emit red light from 600 to 650 nm.

Synthesis and luminescence properties of SrAl_2O_4:Eu^(2+),Dy^(3+) hollow microspheres via a solvothermal co-precipitation method

SrA1204：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 diffxaction （XRD）, scanning and transmission electron microscopy （SEM and TEM） pictures, respectively. The mechanism for the formation of spherical SrAI204：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 SrA1204：Eu2＋,Dy3. hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.