Synthesis and luminescence characteristics of terbium（III） activated NaSrBO3

The thermoluminescence (TL) and photoluminescence (PL) properties of the phosphor NaSrBO 3 :Tb 3+ were reported and discussed. The combustion technique was used for the synthesis of polycrystalline samples of NaSrBO 3 :Tb 3+ . The TL glow curve of the compound had a simple structure with a single peak at 434 K. TL sensitivity of the phosphor was found to be more than that of (LiF:Mg,Cu,P). The TL glow curve was studied as a function of concentration of dopant and dose of gamma ray irradiation. The kinetic parameters of the thermoluminescence of NaSrBO 3 : Tb 3+ were calculated employing the peak shape method. The photoluminescence (PL) properties of Tb 3+ doped in NaSrBO 3 were studied over the 200-400 nm excitation range. The excitation spectra of NaSrBO 3 :Tb 3+ consisted of single narrow band peaking at about 236 nm. The emission spectra monitored at 236 nm excitation consisted of a series of sharp lines peaking at 489, 544, 586 and 622 nm corresponding to the 5 D 4 → 7 F j (j=3,4,5,6) transitions within the 4f 8 configurations of Tb 3+ .     

Preparation! of High Color Rendering Index Phosphor（Gd, Ce, Tb） （Mg, Mn） B5O10

The Ce^3 , Tb^3 and Mn^2 co-activated high color rendering index phosphor (Gd,Ce,Tb)(Mg, Mn)B5O10 was synthesized by ceramic method.The effects of synthetic conditions, such as the amount of boracic acid, Tb/Ce ratio, the concentration of hydrogen in nitrogen, the calcination temperature, on the luminescence properties were studied. It is shown that the high rendering index phosphor can be obtained when the amount of of boracic acid is added in 8% extra,     

Role of monovalent co-dopants on the PL emission properties of YAI3（BO3）4：Ce3＋ phosphor

The cerium （Ce3＋） doped yttrium aluminium borate （YAB） phosphor was synthesized by modified solid state reaction. The phosphor＇s phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra. By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm. The UV emission of the phosphor originated due to Ce3＋ ions at the yttrium site and violet-blue emission owing to Ce3＋ ions at non-regular sites viz., A13＋ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions （K＋, Na＋, and F） were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB：Ce3＋ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.     

Synthesis,characterization and TL properties of SrSO_4:Dy,Tb nanocrystalline phosphor

SrSO4:Dy,Tb nanocrystalline with crystalline size in the range of 44–54 nm was prepared by co-precipitation method followed by thermal treatment and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX) and UV-visible spectrometry. Our results provided direct evidence of incorporation of impurities into nanocrystalline SrSO4. The thermoluminescence(TL) properties of SrSO4:Dy,Tb nanocrystalline pellets irradiated with gamma rays at different doses were studied. The TL glow curve of SrSO4:Dy,Tb nanocrystalline pellets had a prominent peak at around 490 K and a small peak at around 430 K. The major peak in the TL glow curve was almost resolved from other peaks, which was analyzed using Chen's peak shape method to determine the TL kinetic parameters such as activation energy, E and kinetic order, b. The intensity of main dosimetric peak of SrSO4:Dy,Tb nanocrystalline pellets at around 490 K increased linearly with the increase in gamma dose. The TL response was linear in the range of 0.1–7 kGy. These properties made it a candidate as a dosimeter to be used for estimating the high dose of gamma rays.     

Citrate sol-gel combustion preparation and photoluminescence properties of YAG:Ce phosphors

Yellow-emitting YAG:Ce3+ nanocrystalline phosphors were prepared by citrate sol-gel combustion method using citric acid as the fuel and chelating agent. The influence of mole ratio of citric acid to metallic ions (MRCM), pH value of the solution, calcination temperature and Ce-doped concentration on the structures and properties of as-prepared powders were investigated in detail. Higher crystallinity and better luminescence performance powders were obtained at MRCM=2, pH=3 and the calcination temperature of 1200 °C. The phosphors exhibited the characteristic broadband visible luminescence of YAG:Ce. The optimum concentration of Ce3+ was 1.0 mol.%, and the concentration quenching was derived from the reciprocity between electric dipole and electric quadrupole (d-q). Especially, the pH value of the solution was a key factor to obtain a stable sol-gel system and then obtain pure and homogeneous rare earth ions doped YAG phosphors at a lower tem-perature. The Y3Al5O12:Ce0.03 phosphor with optimized synthesis-condition and composition had a similar luminescence intensity with the commercial phosphor YAG:Ce.     

Role of monovalent co-dopants on the PL emission properties of YAl_3(BO_3)_4:Ce~(3+) phosphor

The cerium(Ce3+) doped yttrium aluminium borate(YAB) phosphor was synthesized by modified solid state reaction. The phosphor's phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra.By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm.The UV emission of the phosphor originated due to Ce3+ ions at the yttrium site and violet-blue emission owing to Ce3+ ions at non-regular sites viz., Al3+ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions(K+, Na+, and F–) were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB:Ce3+ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.     

Luminescent properties of SrSi2N2O2:Ce3+,Tb3+-a potential phosphor for white light emitting diodes

Ce3+ and Tb3+ co-doped SrSi2N2O2 phosphors were prepared by solid-state reaction. The X-ray diffraction pattern exhibited that the phosphor consisted mainly of oxygen-rich SrSi2N2O2. The optical properties of SrSi2N2O2:Ce3+, SrSi2N2O2:Tb3+ and SrSi2N2O2:Ce3+,Tb3+ were studied, respectively. The emission intensity of Tb3+ at 541 nm was remarkably enhanced by Ce3+ in SrSi2N2O2:Ce3+,Tb3+ phosphor, which was attributed to the energy transfer from Ce3+ to Tb3+. The chromaticity coordinates of phosphors were investigated as a function of Tb3+ concentration. When the Ce3+ and Tb3+ concentrations were 0.02 and 0.18 mol per formula unit, respectively, the chromaticity coordinate was (0.257, 0.337) in the CIE 1931 chromaticity diagram. SrSi2N2O2Ce3+,Tb3+ phosphors could be used for white light emitting diodes.     

Luminescence properties of SrB4O7：Sm^2＋ for light conversion agent

A deep red-emitting SrB4O7:Sm2+ phosphor for light conversion agent was synthesized by the conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation of SrB4O 7:Sm2+ materials. Results of luminescence properties showed that the phosphor could be efficiently excited by the UV-vis light region from 250-500 nm, and it exhibited deep red (685 nm) emission corresponding to 5D0 → 7F0 transition of Sm 2+ . The critical quenching concentration of Sm 2+ in SrB4O7 :Sm 2+ phosphor was about 0.05, and the corresponding concentration quenching mechanism was verified to be the dipole-dipole interaction according to the Dexter’s theory. The decay times had few alterations with different concentrations in SrB4O7:xSm 2+ phosphor.     

Sm-doped CsBr crystal as a new radio-photoluminescence(RPL) material

Radio-photoluminescence(RPL) is a phenomenon seen in luminescent materials in which the appearance of new photoluminescence(PL) emission is induced by an incident ionizing radiation such as X-rays; and the signal is stable even after the irradiation and during the PL measurement. Since the induced PL intensity is proportional to the irradiation dose, the RPL can be used in radiation measurements. The distinct advantage of RPL over the conventional thermally- or photo-stimulated luminescence(abbreviated as TSL or PSL) dosimeters is the stability of response signal. With an RPL detector, it allows us to readout the signal multiple time without signal fading. In this work, we discovered that CsB r:Sm showed an RPL phenomenon by X-ray irradiation, and we characterized this new material as an RPL detector. While the sample showed PL emissions mainly in the visible range, after an X-ray irradiation additional emissions could be observed in the red to near-infrared range around 650–850 nm and 900–1000 nm and longer. The RPL response was fairly stable overall, but very interestingly the 650–850 nm signal slightly increased while the 900–1000 nm decreased during PL readout. The dynamic range was confirmed over 1–10~4 mG y with linear response.     

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.     

Thermoluminescence Characteristics of SrB6 O10:Tb

SrB6O10:Tb phosphor was synthesized by high-temperature solid state reaction. The influences of Ce or Li as a co-dopant, Tb concentration and irradiation dose exposure on TL of SrB6O10:Tb were investigated. Results show that Ce or Li as a co-dopant can not improve the sensitivity of SrB6O10:Tb phosphor. TL response depends on Tb concentration and 0.02 is the optimum in the concentration range from 0.01 to 0.10. Using the optimum Tb concentration, we calculated the kinetic parameters of SrB6O10:Tb employing the peak shape method, and suggestedthe phosphor obeying the second order kinetics. TL emission intensity is linearly dependent on the irradiation dose withinthe dose range of 50 ～ 200 Gy.The characteristic Tb3 ion emission was observed in TL emission spectrum.     

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.     

Thermoluminescence characteristics of NaSr4（BO3）3：Ce^3＋ under β-ray irradiation

The thermoluminescence (TL) properties of Ce3+ doped NaSr4(BO3)3 phosphor under the β-ray irradiation were reported. The polycrystalline sample was synthesized by high temperature solid-state reaction. The TL glow curve of NaSr4(BO3)3:Ce3+ phosphor was com-posed of only one peak. TL kinetic parameters of NaSr4(BO3)3:Ce3+ were deduced by the peak shape method, the activation energy (E) was 0.590 eV and the frequency factor was 1.008×106s-1. TL dose response was linear in the range of measurement. The 3-dimensional (3D) TL emission spectrum was also recorded, the emission spectrum consisted of two bands located at 441 and 479 nm respectively, corresponding to the characteristic 4f05d1→2F(5/2,7/2) transitions of the Ce3+ ion. The fading behavior of the NaSr4(BO3)3:Ce3+ phosphor over a period of 15 d was also studied.     

Luminescent Properties of BaMgAl10O17： Eu2＋ Phosphors Coated with Y2SiO5

BaMgAl10O17： Eu^2＋ phosphors was prepared by the solid-reaction method. Y2SiO5 was coated uniformly on the surface of phosphor by the surface-coated method, and the luminescent and deterioration properties were discussed. The XRD and SEM results show that Y2SiO5 film is produced on the surface of BAM phosphor. The emission spectrum analysis shows that the peak of the phosphor does not change after coating. The two phosphors were applied to lamps and the deterioration was tested at different ignited time. The keep ratio of luminous flux of the phosphor coated with Y2SiO5 is higher than that of the uncoated phosphor.     

Luminescent properties of β-Lu2Si2O7:RE(RE=Ce, Tb) nanoparticles by sol-gel method

Nanoscale RE³⁺ (RE=Ce, Tb) doped and codoped lutetium pyrosilicate Lu₂Si₂O₇ (LPS) phosphors were prepared by using the sol-gel method. Heat treatment was performed in the temperature range from 900 to 1100 °C. The crystal structure was analyzed by X-ray diffraction (XRD). The results showed that the β-type structure of LPS was obtained at 1100 °C. The excitation spectra in the UV and VUV ranges and the emission spectra of the samples were measured at room temperature, and their luminescent properties were studied. The energy transfer from Ce³⁺ to Tb³⁺ in the codoped samples were observed and discussed.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3：Eu^3＋ phosphor

The Gd2O2CO3：Eu^3＋ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet （VUV） region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer （CT） of Gd^3＋-O2^- were observed for Gd2O2CO3：Eu^3＋. Under 172 nm excitation, Gd2O2CO3：Eu^3＋ exhibited strong red emission with good color purity, indicating Eu^3＋ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3：Eu^3＋ was （x=0.652, y=0.345）. The photoluminescence quenching concentration of Eu^3＋ excited by 172 nm for Gd2O2CO3：Eu^3＋ was about 5%. Gd2O2CO3：Eu^3＋ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.