A novel red-emitting phosphor, KAl1-xPO4Cl:Eux(3+) (0.1 ≤ x ≤ 1.0).

A series of phosphors KAl1-xPO4Cl:Eux(3+) (0.1 ≤ x ≤ 1.0) was synthesized using a facile combustion method using urea as a fuel and their structural, morphological and photoluminescence properties were investigated. It was found that the particle size was in the range of 1-2 µm with an irregular shape. The f-f transitions of Eu(3+) in the host lattice were assigned and discussed. The excitation and emission spectra indicated that this phosphor can be efficiently excited by ultraviolet (395 nm), and exhibit reddish orange emission corresponding to the (5)D0 →(7)FJ (J = 0, 1, 2) transitions of Eu(3+). The impact of the Eu(3+) concentration on the relative emission intensity was investigated, and the best doping concentration is 0.5. The present study suggests that the KAl0.5PO4Cl:Eu0.5(3+) phosphor is a strong candidate as a red component for phosphor- converted white light-emitting diodes (LEDs).

Impact of temperature on Na2 Sr(PO4)F:Eu3+ phosphor.

In this article, we report the synthesis of Na2 Sr1-x (PO4)F:Eux phosphor via a combustion method. The influence of different annealing temperatures on the photoluminescence properties was investigated. The phosphor was excited at both 254 and 393 nm. Na2 Sr1-x (PO4)F:Eux (3+) phosphors emit strong orange and red color at 593 and 612 nm, respectively, under both excitation wavelengths. Na2 Sr1-x (PO4)F:Eux (3+) phosphors annealed at 1050°C showed stronger emission intensity compared with 600, 900 and 1200°C. Moreover, Na2 Sr1-x (PO4)F:Eux (3+) phosphor was found to be more intense when compared with commercial Y2 O3:Eu(3+) phosphor.

Energy transfer in M5(PO4)3 F:Eu²âº,Ce³âº (M = Ca and Ba) phosphors.

M5(PO4)3F:Eu(2+) (M = Ca and Ba) co-doped with Ce(3+) phosphors were successfully prepared by the combustion synthesis method. The introduction of co-dopant (Ce(3+)) into the host enhanced the luminescent intensity of the M5(PO4)3F:Eu(2+) (M = Ca and Ba) efficiently. Previously, we have reported the synthesis and photoluminescence properties of same phosphors. The aim of this article is to report energy transfer mechanism between Ce(3+) ➔Eu(2+) ions in M5(PO4)3F:Eu(2+) (M = Ca and Ba) phosphors, where Ce(3+) ions act as sensitizers and Eu(2+) ions act as activators. The M5(PO4)3F:Eu(2+) (M = Ca and Ba) co-doped with Ce(3+) phosphor exhibits great potential for use in white ultraviolet (UV) light-emitting diode applications to serve as a single-phased phosphor that can be pumped with near-UV or UV light-emitting diodes.

Solution combustion synthesis of Dy(3+) and Ce(3+) activated Na2ZnSi2O6 phosphors.

Here we first time reported Dy(3+) and Ce(3+) luminescence in novel Na2ZnSi2O6 phosphors by solution combustion synthesis prepared at 550 °C. Emission spectra of Na2ZnSi2O6:Dy(3+) phosphor was observed at 470 nm and 576 nm keeping excitation wavelength at 350 nm, where as Na2ZnSi2O6:Ce(3+) shows emission band at 452 nm monitoring excitation at 354 nm. XRD analysis was carried out to observe crystalline nature of the prepared phosphor.

Synthesis and photoluminescence of novel Ca(1-x)MgP2O7:xEu(3+) pyrophosphate phosphor for near ultraviolet light emitting diodes.

We studied the microstructure and photoluminescence properties of Ca(1-x)MgP2O7:xEu(3+) (0.01 ≤ x ≤ 0.2) phosphors, considering Eu(3+) content. The Ca(1-x)MgP2O7:xEu(3+) phosphors crystallized in the monoclinic structure, belonging to the space group of P2(1)/n. The Ca(1-x)MgP2O7:xEu(3+) phosphors showed a nanocrystalline nature. In the FT-IR and Raman spectra, the stretching vibrations of PO3 and P-O-P groups in (P2O7)(4-) were observed. The amount of Eu(3+) content significantly affected the magnitude of the excitation and emission intensities. The excitation intensity at 393 nm and the emission intensity at 605-628 nm were increased with an increase in Eu(3+) content up to x = 0.1 and then decreased with further increasing Eu(3+) content. The strong emission intensity under near ultraviolet excitation makes it possible red phosphor for generating white light based on LEDs.

Synthesis and photoluminescence of novel NaLi2PO4:Tb(3+) nanophosphors for near-ultraviolet excited light emitting diodes.

A series of Tb(3+)-activated NaLi2PO4 novel nano-crystalline phosphors was synthesized by the solution combustion method. The prepared Na(1-x)Li2PO4:xTb(3+) (0.01 ≤ x ≤ 0.1) phosphors crystallized in the orthorhombic crystal structure. Its effective absorption in the near ultraviolet range allowed highly efficient green emission. The Na(1-x)Li2PO4:xTb(3+) phosphors showed characteristic (5)D4 --> (7)FJ (J = 3, 4, 5, and 6) transitions of Tb(3+), i.e., (5)D4 --> (7)F6 (488 nm), (5)D4 --> (7)F5 (545 nm), (5)D4 --> (7)F4 (583 nm), and (5)D4 --> (7)F3 (622 nm). The Na0.95Li2PO4:0.05Tb(3+) phosphor showed the most excellent emission efficiency. The present work suggests that the Na0.95Li2PO4:0.05Tb(3+) is a potential green-emitting phosphor for near ultraviolet excited light emitting diodes.

Synthesis and luminescence properties of Eu(2+) activated Ca2P2O7 pyrophosphate phosphor.

In the present study, calcium pyrophosphate activated with Eu(2+) rare earth ions prepared by solid state diffusion and confirmed by XRD. An average crystallite size is found out to be in sub-micrometer range of 2-5 µm from SEM study. FTIR spectra suggest that Ca2P2O7 material belongs to the diphosphate family. The PL spectroscopic characterizations of the prepared phosphors were performed using excitation and emission spectra. Photoluminescence spectra of Ca2P2O7:Eu(2+) pyrophosphate phosphor shows emission at 426 nm when excited at 356 nm.

Synthesis and effect of Ce and Mn co-doping on photoluminescence characteristics of Ca6AlP5O20:Eu novel phosphors.

A series of Ca6AlP5O20 doped with rare earths (Eu and Ce) and co-doped (Eu, Ce and Eu,Mn) were prepared by combustion synthesis. Under Hg-free excitation, Ca6AlP5O20:Eu exhibited Eu(2+) (486 nm) emission in the blue region of the spectrum and under near Hg excitation (245 nm), Ca6AlP5O20:Ce phosphor exhibited Ce(3+) emission (357 nm) in the UV range. Photoluminescence (PL) peak intensity increased in Ca6AlP5O20:Eu,Ce and Ca6AlP5O20:Eu, Mn phosphors due to co-activators of Ce(3+) and Mn(2+) ions. As a result, these ions played an important role in PL emission in the present matrix. Ca6AlP5O20:Eu, Ce and Ca6AlP5O20:Eu, Mn phosphors provided energy transfer mechanisms via Ce(3+) → Eu(2+) and Eu(2+) → Mn(2+), respectively. Eu ions acted as activators and Ce ions acted as sensitizers. Ce emission energy was well matched with Eu excitation energy in the case of Ca6AlP5O20:Eu, Ce and Eu ions acted as activators and Mn ions acted as sensitizers in Ca6AlP5O20:Eu, Mn. This study included synthesis of new and efficient phosphate phosphors. The impact of doping and co-doping on photoluminescence properties and energy transfer mechanisms were investigated and we propose a feasible interpretation.

Luminescence in Li3 Al 2 (PO4)3 :Eu(2+).

A series of efficient Li3 Al 2 (PO4)3 :Eu(2+) novel phosphors were synthesized by the facile combustion method. The effects of dopant on the luminescence behavior of Li3 Al 2 (PO4)3 phosphor were also investigated. The phosphors were characterized by X-ray diffraction, field emission scanning electron microscope and photoluminescence techniques. The result shows that all samples can be excited efficiently by near-ultraviolet excitation under 310 nm. The emission was observed for Li3 Al 2 (PO4)3 :Eu(2+) phosphor at 425 nm, which corresponded to the d → f transition. The concentration quenching of Eu(2+) was observed in Li3 Al 2 (PO4)3 :Eu(2+) when the Eu concentration was at 0.5 mol%. The prepared powders exhibited intense blue emission at the 425 nm owing to the Eu(2+) ion by Hg-free excitation at 310 nm (i.e., solid-state lighting excitation). Consequently, the availability of such a phosphor will significantly help in the development of blue-emitting solid-state lighting applications.

A novel reddish-orange phosphor, NaLi2PO4:Eu3+.

A series of Eu(3+)-activated NaLi(2)PO(4) novel phosphors was synthesized by the solid-state reaction method. The X-ray diffraction (XRD) and photoluminescence (PL) properties of these phosphors were investigated at room temperature. The excitation spectra indicate that these phosphors can be effectively excited by near-UV (370-410 nm) light. The emission spectra exhibit strong reddish-orange performance, which is due to the (5)D(0) → (7)F(J) transitions of Eu(3+) ions. The orange emission from transition (5)D(0) → (7)F(1) is dominant over that of (5)D(0) → (7)F(2.) The concentration quenching of Eu(3+) was observed in NaLi(2)PO(4):Eu(3+) when the Eu concentration was at 1 mol%. The impact of doping Eu(3+) and photoluminescence properties were investigated and we propose a feasible interpretation.

Thermoluminescence and photoluminescence in the NaCaPO4:Dy3+ phosphor.

Dy(3+)-doped NaCaPO(4) phosphor was synthesised at an initiating combustion temperature of 600°C, using urea as the fuel. The crystallinity of the phosphor was investigated by using X-ray diffraction. The photoluminescence and thermoluminescence (TL) behaviours of NaCaPO(4):Dy(3+) phosphor was also studied. It has a simple TL glow curve structure, which does not change when exposed to gamma-rays. A TL glow peak is observed at 230°C and TL intensity is around 1.15 times more compared with commercial CaSO(4):Dy TLD phosphor. The TL characteristics of the phosphor prepared show that it has good sensitivity, linear response with gamma-rays exposure, emission in the blue-yellow regions of the spectrum, negligible fading and excellent reusability. These results make Dy(3+)-doped NaCaPO(4) phosphor attractive for TLD applications.

Luminescence in Li2Sr2Al2PO4F9:Dy3+ - a novel nanophosphor.

Earlier research has revealed numerous advantages of the wet chemical method in reaction acceleration, yield improvement, enhanced photoluminescence properties and the evolution of new material phases. In the present study the novel nanophosphor Li(2)Sr(2)Al(2)PO(4)F(9):Dy(3+) was synthesized by a one-step wet chemical method. Formation of single-phase compounds was confirmed by X-ray diffraction (XRD) and characterized by photoluminescence (PL) and transmission electron microscopy (TEM) techniques. The average diameter of the particles was calculated from the TEM image as ca. 20 nm. The synthesized nanophosphor exhibited intense blue and yellow emissions at 482 and 575 nm, respectively, owing to the Dy(3+) ion, by Hg-free excitation at 387 nm, i.e. solid-state lighting excitation. The results obtained showed that phosphors have the potential for applications in the lamp industry.

5d-4f transition in new phosphate-based phosphors.

The preparation of Ce(3+)-doped Sr(6) AlP(5) O(20) and Ba(6) AlP(5) O(20) by a combustion method is described. Formation of compounds was confirmed by X-ray diffraction (XRD) analysis. The photoluminescence (PL) emission spectra were observed at 355 nm when excited at 307 nm for the various concentrations. The PL emission spectra of phosphors showed strong Ce(3+) emission due to the 5 d → 4f transition of Ce(3+) ions. The Ce(3+) emission intensity in Sr(6) AlP(5)O(20):Ce phosphor was higher than that in Ba(6) AlP(5)O(20):Ce and it may be useful for scintillation applications.

Luminescence in Dy3+ and Eu3+ activated K3Al2(PO4)3.

The Dy(3+) and Eu(3+) activated K(3)Al(2) (PO(4))(3) phosphors were prepared by a combustion synthesis. From a powder X-ray diffraction (XRD) analysis the formation of K(3)Al(2) (PO(4))(3) was confirmed. In the photoluminescence emission spectra, the K(3)Al(2)(PO(4))(3):Dy(3+) phosphor emits two distinctive colors: blue and yellow whereas K(3)Al(2)(PO(4))(3):Eu(3+) emits red color. Thus the combination of colors gives BYR (blue-yellow-red) emissions can produce white light. These phosphors exhibit a strong absorption between 340 and 400 nm which suggest that present phosphor is a promising candidate for producing white light-emitting diodes (LED).

Effect of temperature on intense green emitting Na2Ca(PO4)F:Mn²âº phosphor.

An intense green luminescent Na2Ca(PO4)F:Mn²âº phosphor has been prepared at high temperature by reduction treatment in a charcoal environment. The emission band of Mn²âº was obtained at around 522 nm (green) under 259 nm excitation. Enhancement in emission intensity arising from the thermal treatment is reported. The intense emission of the spectrum was assigned to electronic transitions 4T1 → 6A1 of Mn²âº ions. Intense PL emission suggested that temperature employed plays an important role in the present matrix. X-ray diffraction pattern, photoluminescence and morphology by SEM of the host lattice of phosphors at different temperatures have been reported in this paper. The results obtained show that the present phosphor has potential for application in green emitting phosphors for the lamp industry.