Search

The phosphors LaPO 4 (Lanthanum phosphate) doped with Ce(III)/Ce 3+ and co-doped with Ce 3+ -Nd 3+ and Ce 3+ -Yb 3+ were effectively synthesized by conventional solid state reaction method. The prepared samples were characterized by powder X-ray diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied by spectrophotometers in near infrared (NIR) and ultraviolet visible (UV–VIS) region. Additionally the luminescence time decay curves of samples were investigated to confirm energy transfer (ET) process. The Ce 3+ -Nd 3+ ion co-doped LaPO 4 phosphors can convert a photon of UV region (278 nm) into photons of NIR region (1058 nm). While Ce 3+ -Yb 3+ ion doped LaPO 4 phosphors convert photons of UV region (278 nm) into photons of NIR region (979 nm). The Ce 3+ ion acts like sensitizer and Nd 3+ /Yb 3+ ions act as activators. Both kinds of emissions are suitable for improving spectral response of solar cells. [ABSTRACT FROM AUTHOR]

The materials LiSrVO 4 (LSV) were successfully synthesized by co-precipitation method varying the concentration of Yb 3+ ions from 0 to 0.01 mol. It was characterize by powder X-ray powder diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied by spectrophotometers in near infra red (NIR) and ultra violet visible (UV–Vis) region. The Yb 3+ ion doped lithium strontium vanadate (LiSrVO 4 ) phosphors that can convert a photon of UV region (343 nm) into photons of NIR region (988 nm). Hence this phosphor could be used as a quantum cutting (QC) luminescent convertor in front of crystalline silicon solar cell (c-Si) panels to reduce thermalization loss due to spectral mismatch of the solar cells. The theoretical value of quantum efficiency (QE) was calculated from steady time decay measurement and the maximum efficiency approached up to 174.45%. [ABSTRACT FROM AUTHOR]

Abstract: The red emitting phosphor NaSrBO3:Eu 3+ is synthesised by simple, time saving, economically modified method of solution combustion synthesis at comparatively lower temperature using urea as fuel. X-ray power diffraction (XRD) analysis confirmed the formation of the said phosphor. Photoluminescence measurements showed that the phosphor exhibited emission peak with good intensity at −614nm, corresponding to 5D0–7F2 (614nm) red emission andweak 5D0–7F1 (593nm) orange emission. The excitation spectra monitored at 614nm show broad band from 250 to 350nm ascribed to O–Eu charge-transfer (CTB) transition and the other peaks in the range of 350–410nm originated from f–f transitions of Eu3+ ions. The strongest band at 394nm can be assigned to 7F0–5L6 transition of Eu3+ ions due to the typical f–f transitions within Eu3+ of 4f6 configuration. The latter lies in near ultraviolet (350–410nm) emission of UV LED. For the excitation wavelength of 394nm the emission intensity increases initially with the increase of Eu3+ concentration and reaches to the maximum at x=0.09.The concentration quenching observed after that is mainly due to quadrupole–quadrupole interaction. The as synthesised phosphor NaSrBO3:Eu 3+ by this method shows CIE colour coordinates of (0.62,0.34) with good intensity. [Copyright &y& Elsevier]

This work offered study the rare earth doped LiBaBO 3 phosphor to reveal the luminescence properties in this material. X-Ray diffraction is used to confirm the crystal structure of this material made by solution combustion synthesis route. A Photoluminescence (PL) measurement shows the phosphor exhibited intense emission at 592 nm and 615 nm respectively corresponding to 5D 0 → 7F 1 and 5D 0 → 7F 2 transitions of Eu 3+ on excitation with optimum 394 nm wavelengths. The remaining excitation peaks at 381 and 465 nm with broad band 200–310 nm are also shown in the excitation spectra. Varying the irradiation dose of gamma radiation as well as rare earth activator quantity, its thermoluminescence (TL) spectra is measured. A single TL glow peak is obtained at 170 °C with a shoulder around 266 °C for the heating rate of 5 °C/s a. After deconvolution, activation energy and frequency factors are calculated for two peaks P 1 and P 2 . The linear dose response is sketch graphically which prove this phosphor to be useful in the category of new dosimetry materials. [ABSTRACT FROM AUTHOR]

Gd 3+ activated inorganic lanthanum phosphate (LaPO 4 ) has been successfully synthesized using re-crystallization method. The crystal structure and the phase purity of samples were characterized using powder X-ray diffractometer. The surface morphology was studied using Scanning Electronic Microscope (SEM). The photoluminescence spectra was studied at room temperature. The excitation spectra of Gd 3+ activated phosphor LaPO 4 monitored at 312 nm shows strong absorption at 275 nm. Phosphor emitted at 312 under the excitation of 275 nm due to 6 P J → 8 S 7 / 2 transition of Gd 3+ ions. Optimum concentration of Gd 3+ ions in the prepared phosphor was found to be 0.04 mol. For this concentration the critical distance R 0 was calculated to be 15.37 Å. Finally, the Stokes shift for the synthesized phosphor LaPO 4 : Gd 3+ was calculated to be 4312 cm −1 . [ABSTRACT FROM AUTHOR]

Yttrium Gadolinium Pyrosilicate Y 2-x Gd x Si 2 O 7 :Eu 3+ (x = 0.05, 0.10, 0.15) phosphor powder was prepared by facile and time efficient modified combustion method for the first time. The phosphor was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence excitation (PLE) and emission (PL) spectroscopy and color chromaticity coordinates. XRD revealed the monoclinic crystal structure with space group P1¯. The crystallite size was calculated by Williamson-Hall (W–H) analysis. Nanoplates-like morphology was observed in FESEM analysis with size in the range 50–80 nm. TEM images confirmed the particle size and shape. Upon excitation by 254 nm UV light, the phosphor showed the characteristic red emission peaks at 589 nm and 613 nm corresponding to 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 transitions respectively. It was observed that the nanocrystalline phosphor Y 2-x Gd x Si 2 O 7 :Eu 3+ can be tuned to emit orange to red color by adjusting the ratio Y/Gd. This phosphor thus can be a potential candidate as orange to red color emitting tunable nanocrystalline phosphor for optical devices. [ABSTRACT FROM AUTHOR]

The polycrystalline sample of bio-nanomaterial α-Ca 2 P 2 O 7 :Eu 3+ was prepared by employing modified solution combustion synthesis method. The prepared sample was confirmed by X-ray diffraction (XRD) technique and Photoluminescence (PL) spectra. The Scanning Electron Microscope (SEM) shows the nanostructure of this phosphor. By exposing with gamma-rays its thermoluminescence (TL) properties were recorded. Thermoluminescence glow curves of α-Ca 2 P 2 O 7 :Eu 3 + phosphor shows three distinct glow peaks at 160 °C while higher temperature peaks at 275 °C and 322 °C, respectively, for the heating rate of 5 °C/s. The kinetic parameters including activation energy ( E ) and frequency factor ( s ) were calculated using peak shape method for both the peaks of given phosphor. The phosphor was found to be comparable (116%) sensitive to that of commercially available LiF: Mg, Cu, P (TLD-100H) phosphor. The effect of dose variation on α-Ca 2 P 2 O 7 :Eu 3+ was found to be linear up to 25 Gy dose. [ABSTRACT FROM AUTHOR]

Photoluminescence properties of a novel UV emitting phosphor Sr 2 Mg(BO 3 ) 2 :Pb 2+ ,Gd 3+ with varying concentration of Pb 2+ and Gd 3+ were studied. Crystal structure and co-ordination of prepared phosphor was confirmed using powder X-ray diffraction and FT-IR. SEM images of prepared powder samples show the irregular grains with agglomeration phenomena. Under the excitation of Hg line of 254 nm phosphor materials show two emissions at 313 nm and 330 nm, which could be applicable in phototherapy for combination therapy of narrowband UVB plus PUVA. [ABSTRACT FROM AUTHOR]

The series of (Y (1 − x ) Gd x )BO 3 : 0.01 Eu 3+ phosphors was successfully synthesized by precipitation method. All phosphors were characterized by X-ray diffraction pattern (XRD) for crystalline structure and UV–vis, photoluminescence (PL) and decay curves measurements were carried out to characterize their optical properties. The PL emission spectra of (Y (1 − x ) Gd x )BO 3 : 0.01 Eu 3+ phosphors indicated that red–orange (595 nm) color could be well excited by 233 nm. The effect of x (Gd 3+ ions) increases in (Y (1 − x ) Gd x )BO 3 : 0.01 Eu 3+ on PL properties has been examined. The results showed that increment of x molar concentration in (Y (1 − x ) Gd x )BO 3 : 0.01 Eu 3+ would lead to a outstanding enhancement of fluorescence intensity. The chromaticity coordinates (CIE) were calculated. The R/O ratio of the luminescence intensity of 5 D 0 → 7 F 2 (red) to 5 D 0 → 7 F 1 (orange) transitions were very well increases with the increasing percentage of Gd 3+ ions in (Y (1 − x ) Gd x )BO 3 : 0.01 Eu 3+ phosphor. [ABSTRACT FROM AUTHOR]

Highlights: [•] New red phosphors (Y1 − x ,Gd x )BaB9O16:0.03Eu3+ y were prepared by combustion technique. [•] Synthesized material were characterized by TG-DTA, powder XRD and FE-SEM and UV, VUV PL. [•] Shifting of dominant emission with influence of Gd concentration has been demonstrated. [•] The intermediate role of Gd3+ion for energy transfer and optimum concentration for color purity. [•] CIE x,y co-ordinates of phosphor have good agreement with NTCL for flat panel, PDP display color. [Copyright &y& Elsevier]

Highlights: [•] (Y,Gd)Al3(BO3)4:Eu3+, Na3La2(BO3)3:Tb3+and BaMgAl10O16:Eu2+ reported by CST. [•] Nano-particles of BaMgAl10O16:Eu2+ were obtained by combustion synthesis. [•] Characterized by XRD, FE-SEM, PL properties by UV and VUV Spectrophotometer. [•] CIE co-ordinates are close to NTCL, for PDP display color. [ABSTRACT FROM AUTHOR]

LaB 3 O 6 :Bi,Gd and YBaB 9 O 16 :Bi,Gd phosphors were synthesized by the combustion synthesis method. The phase analysis of all synthesized materials was determined using the powder X-ray diffraction (XRD). Photoluminescence properties were systematically investigated. Both the samples show the characteristic narrow-band UVB emission of Gd 3+ ions ( 6 P J → 8 S 7/2 ). The maximum intensity of luminescence in synthesized materials was investigated. The energy transfer mechanism was studied using Bi 3+ as sensitizer. The stoke shift in these two phosphors were calculated to be 7060 cm −1 and 5680 cm −1 , respectively. The phosphors could be excellent phototherapy phosphor materials. [ABSTRACT FROM AUTHOR]

Highlights • Dy:LKBO single crystal was grown by Czochralski technique and characterized. • Characteristic emissions of Dy3+ ions were observed in PL analysis. • TL glow curve of Dy:LKBO crystal exhibits glow peak at 181 °C. • TL intensity increases linearly with increasing the gamma dose. • The gamma irradiation storage stability was excellent for grown crystal. Abstract A tissue-equivalent TL dosimeter single crystal of Dy:LiKB 4 O 7 (Dy:LKBO) was grown by the Czochralski technique. Phase purity of the grown crystal was confirmed by powder XRD analysis. The optical bandgap (E g) of the grown crystal was calculated from UV–Vis-NIR spectral analysis to be 5.1 eV. Photoluminescence spectrum of Dy:LKBO crystal reveals prominent emission in green region when excited with UV light (346 nm). The grown crystal was subjected to γ-irradiation for dose ranges of 26, 52, 78, 104, 130 and 156 Gy using Co-60 source. The dose range was selected according to the personal and clinical requirements standards. The thermoluminescence analyses of γ-irradiated crystalline samples were performed; the glow curve measurement, fading effect, dose-response and reusability were analyzed and discussed in detail. The experimental results confirm that the Dy:LKBO single crystal can act as a potential material in TL dosimetry applications. [ABSTRACT FROM AUTHOR]

Rare earth (Dy 3+ , Sm 3+ ) ions doped and undoped NaMgSO 4 F polycrystalline phosphors were synthesized by simple route of re-crystallization method. The crystal structure of doped and undoped material was characterized using X-ray diffraction (XRD). Optical absorption and emission analysis and decay curves were carried out to find efficient energy transfer within co-doped phosphors. The multicolor emission from co-doped materials at characteristic excitation suggests a well defined approach towards energy transfer emission for white light emission (W-LEDs). [ABSTRACT FROM AUTHOR]

Li 2 B 4 O 7 : Cu-Ag phosphor was synthesized by using solid state method. The Li 2 B 4 O 7 : Cu-Ag phosphor was characterized by using X-ray Diffractions (XRD), optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques. The phosphor Li 2 B 4 O 7 : Cu - Ag shows good OSL sensitivity about 1.3 and 0.86 times than that of commercially available Al 2 O 3 :C and LiMgPO 4 :Tb 3+ , B phosphors respectively. It was found to possess three OSL components and having photoionization cross-sections of 0.267 × 10 −17 , 1.79 × 10 −17 and 6.46 × 10 −17 cm 2 . In TL mode Li 2 B 4 O 7 : Cu - Ag phosphor shows dosimetric peaks around 179 °C and 248 °C. The TL sensitivity was twice than that of Al 2 O 3 : C phosphor. In both the mode (TL/OSL) dose response was nearly in linear range. [ABSTRACT FROM AUTHOR]

The series of Ce 3+ ion doped YAG phosphor have been synthesized by mixed fuel combustion technique. The phase purity and crystalline size of phosphors confirmed by X-ray diffraction (XRD) analysis while surface morphology studied by scanning electron microscopy (SEM). The photoluminescence (PL) studied within 200–700 nm wavelengths. Commission Internationale de l’Eclairage (CIE) co-ordinate of phosphor studied for and found suitable for solid state lighting and white LEDs. The nanometric particle size 15.838 nm and 18.683 nm at 900 °C and 1000 °C, respectively, make the mentioned synthesis method idyllic. [ABSTRACT FROM AUTHOR]

Novel LiAl 7 B 4 O 17 (LABO) phosphor activated with trivalent rare earth ions (RE = Tb, Sm) was synthesized by using solution combustion synthesis. The powder X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), photoluminescence (PL), critical transfer distance ( R c ) and quenching mechanism studies were employed to characterize the samples. Under ultraviolet irradiation of the LiAl 7 B 4 O 17 : Tb 3+ , Sm 3+ phosphors exhibit the typical green ( 5 D 4 → 7 F j = 6, 5, 4 and 3) emission band of the Tb 3+ ions, as well as an orange-red and red ( 4 G 5/2 → 6 H J=5/2, 7/2, 9/2 ) emission bands of the Sm 3+ ions. These results suggest that Tb 3+ and Sm 3+ activated LABO phosphor could be promising in vision of the necessity for solid state lighting applications. [ABSTRACT FROM AUTHOR]

Abstract: One step, wet chemical synthesis of several aluminofluorides is described. Formation of single phase compounds was confirmed by XRD. Ce3+ activation was achieved during the synthesis itself. As prepared powders, without any heat treatment, exhibited intense, characteristic Ce3+ photoluminescence. It is suggested that availability of such powders will greatly facilitate growth of single crystals for applications like scintillators and solid-state lasers. [Copyright &y& Elsevier]

Abstract: Wet chemical synthesis of LiAEAlF6:Eu (AE=Mg, Ca, Sr or Ba) phosphors is described. Formation of single-phase compounds LiCaAlF6 and LiSrAlF6 was confirmed by XRD. LiCaAlF6:Eu and LiSrAlF6:Eu phosphors exhibited broadband emission corresponding to intraconfigurational transition 4f65d1→4f7(8S7/2). LiMgAlF6:Eu exhibits a narrow line emission corresponding to 6P J →8S7/2 transition of 4f7 configuration besides the band emission. LiBaAlF6:Eu, on the other hand, was found to yield predominantly line emission. [Copyright &y& Elsevier]