A series of single-phase broadband white-light-emitting Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
phosphors were prepared by a solid state reaction. The luminescence property, and the crystal and electronic ...structures of the fluorophosphates were studied by photoluminescence analysis, XRD Rietveld refinement and density functional theory calculation (DFT), respectively. Under near ultraviolet excitation in the 250 to 430 nm wavelength range, the phosphors exhibit two emission bands centered at 440 and 556 nm, caused by the Eu
2+
and Mn
2+
ions. By altering the relative ratios of Eu
2+
and Mn
2+
in the compounds, the emission color could be modulated from blue to white. The efficient energy transfer from the Eu
2+
to Mn
2+
ions could be ascribed to the well crystallized host lattice and the facile substitution of Eu
2+
and Mn
2+
for Sr
2+
sites due to similar ionic radii. A series of fluxes were investigated to improve the photoluminescence intensity. When KCl was used as flux in the synthesis, the photoluminescence intensity of Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
was enhanced by 85% compared with no fluxes added. These results demonstrate that the single-phase Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
with enhanced luminescence efficiency could be promising as a near UV-convertible direct white-light-emitting phosphor for WLED applications.
Single-phase Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
phosphors are prepared, showing white-light emission under near UV excitation. The photoluminescence intensity is enhanced by 85% by using KCl as flux. The relationship between photoluminescence and the crystal and electronic structures is studied.
A series of single-phase broadband white-light-emitting Sr sub(5)(PO sub(4)) sub(3)F:Eu super(2+),Mn super(2+) phosphors were prepared by a solid state reaction. The luminescence property, and the ...crystal and electronic structures of the fluorophosphates were studied by photoluminescence analysis, XRD Rietveld refinement and density functional theory calculation (DFT), respectively. Under near ultraviolet excitation in the 250 to 430 nm wavelength range, the phosphors exhibit two emission bands centered at 440 and 556 nm, caused by the Eu super(2+) and Mn super(2+) ions. By altering the relative ratios of Eu super(2+) and Mn super(2+) in the compounds, the emission color could be modulated from blue to white. The efficient energy transfer from the Eu super(2+) to Mn super(2+) ions could be ascribed to the well crystallized host lattice and the facile substitution of Eu super(2+) and Mn super(2+) for Sr super(2+) sites due to similar ionic radii. A series of fluxes were investigated to improve the photoluminescence intensity. When KCl was used as flux in the synthesis, the photoluminescence intensity of Sr sub(5)(PO sub(4)) sub(3)F:Eu super(2+),Mn super(2+) was enhanced by 85% compared with no fluxes added. These results demonstrate that the single-phase Sr sub(5)(PO sub(4)) sub(3)F:Eu super(2+),Mn super(2+) with enhanced luminescence efficiency could be promising as a near UV-convertible direct white-light-emitting phosphor for WLED applications.
A series of Sr7Zr(PO4)6:Tb3+, Eu3+ phosphors of eulytite-type structure have been synthesized via a high temperature solid-state reaction. The crystal structure and luminescence property of the ...samples was systematically investigated by XRD Rietveld refinement, excitation and photoluminescence, respectively. For Tb3+ and Eu3+ ions single doped phosphor, the characteristic emission from f-f transitions of Tb3+ at 544 nm and Eu3+ at 613 nm was observed, while for Tb3+ and Eu3+ co-doped phosphor Sr7Zr(PO4)6:Tb3+, xEu3+, various emission color from green to red can be achieved by trimming the relative ratio of Eu3+ to Tb3+ in Sr7Zr(PO4)6 host. Moreover, a warm white light emission of single phased with CIE coordinates at (0.359, 0.327) and correlated color temperature (CCT) at 4264 K was realized under 374 nm excitation. The energy transfer process from Tb3+ to Eu3+ in Sr7Zr(PO4)6 was verified by fluorescence spectra and decay time, where a resonant type via a dipole-dipole mechanism was demonstrated. In addition, the Sr7Zr(PO4)6:Tb3+, Eu3+ phosphors exhibited an excellent thermal quenching luminescence property owing to the structural stability. These results indicate that Sr7Zr(PO4)6:Tb3+, Eu3+ could be anticipated as color-tunable and direct white-light-emitting phosphor for near-UV-pumped w-LEDs application.
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•A series of single phased warm-white-emissive and color-tunable phosphors were prepared.•The crystal structure and photoluminescence property of the phosphors were systematically investigated.•The energy transfer process from Tb3+ to Eu3+ in Sr7Zr(PO4)6 was verified by fluorescence spectra and decay time.•Excellent thermal quenching property predicts the promising application in near-UV LEDs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A series of La3BW1–x Mo x O9:Eu3+ (x = 0–0.4) polycrystalline powders were prepared by using solid-state reactions. The phase structure, UV–vis absorption spectra, and photoluminescence properties ...were studied as a function of the Mo/W ratio. When Mo6+ ions are incorporated into the lattice, the characteristic sharp lines in the excitation spectra of Eu3+ monitored at 617 nm are prominently enhanced, which join the ligand-to-metal charge transfer (LMCT) band of La3BW1–x Mo x O9:Eu3+ into a broad band ranging from 250 to 450 nm centered at 375 nm. The intensity of the broad excitation band reaches a maximum when the content of Mo6+ ions increases to x = 0.3. On the other hand, the LMCT band around 306 nm decreases and shifts toward the longer wavelength. These features are advantageous to near-UV or blue light GaN-based LED applications. Orbital population analysis by density functional theory calculation (DFT) reveals that the near-UV excitation of La3BW1–x Mo x O9:Eu3+ red phosphor is due to the electronic transition from the O 2p orbital to the W 5d and Mo 4d orbitals, respectively. With the introduction of Mo6+ into the lattice, the band gap of La3BW1–x Mo x O9 becomes narrower than that of the pure phase La3BWO9.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A series of single-phase broadband white-light-emitting Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
phosphors were prepared by a solid state reaction. The luminescence property, and the crystal and electronic ...structures of the fluorophosphates were studied by photoluminescence analysis, XRD Rietveld refinement and density functional theory calculation (DFT), respectively. Under near ultraviolet excitation in the 250 to 430 nm wavelength range, the phosphors exhibit two emission bands centered at 440 and 556 nm, caused by the Eu
2+
and Mn
2+
ions. By altering the relative ratios of Eu
2+
and Mn
2+
in the compounds, the emission color could be modulated from blue to white. The efficient energy transfer from the Eu
2+
to Mn
2+
ions could be ascribed to the well crystallized host lattice and the facile substitution of Eu
2+
and Mn
2+
for Sr
2+
sites due to similar ionic radii. A series of fluxes were investigated to improve the photoluminescence intensity. When KCl was used as flux in the synthesis, the photoluminescence intensity of Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
was enhanced by 85% compared with no fluxes added. These results demonstrate that the single-phase Sr
5
(PO
4
)
3
F:Eu
2+
,Mn
2+
with enhanced luminescence efficiency could be promising as a near UV-convertible direct white-light-emitting phosphor for WLED applications.
A series of phosphors Ca12(0.97−x)Al14O32F2: 0.03Ce3+, xTb3+ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, ...I4¯3d space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca12(0.97−x)Al14O32F2: 0.03Ce3+, xTb3+ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce3+ and a characteristic emission at 544 nm of Tb3+. The emission can be tuned from blue to green by altering the relative ratio of Ce3+ to Tb3+ in the composition. The energy‐transfer mechanism from Ce3+ to Tb3+ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca12Al14O32F2 host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca12(0.97−x)Al14O32F2: 0.03Ce3+, xTb3+ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
A series of phosphors Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in ...cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5 d →4 f transitions of Ce 3+ and a characteristic emission at 544 nm of Tb 3+ . The emission can be tuned from blue to green by altering the relative ratio of Ce 3+ to Tb 3+ in the composition. The energy‐transfer mechanism from Ce 3+ to Tb 3+ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca 12 Al 14 O 32 F 2 host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
