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A novel apatite structure phosphor Ca 9 La(PO 4 ) 5 (GeO 4 )F 2 :Dy 3+ (CLPGF:Dy 3+ ) with a hexagonal lattice in the P 6 3 / m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy 3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ , respectively. The concentration quenching of Dy 3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4 F 9/2 to 6 H 15/2 transition and 4 F 9/2 to 6 H 13/2 transition of Dy 3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy 3+ phosphor is a promising white-emitting candidate for w -LEDs applications. [ABSTRACT FROM AUTHOR]

Single-phase Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ samples with apatite structure have been synthesized via a solid-state reaction method. The phase structure, luminescence properties, lifetime, PL thermal stability, as well as fluorescence decay curves of the samples were investigated. Effective energy transfer occurs from Eu 2+ to Mn 2+ in Ba 10 (PO 4 ) 6 O and a possible mechanism of the energy-transfer from Eu 2+ to Mn 2+ is proposed. The critical distances R c was calculated by concentration quenching and turned out to be about 0.817 nm ( x c =0.21). The CIE and thermally stable luminescence behaviors of Ba 9.94 (PO 4 ) 6 O:0.06Eu 2+ phosphor were also studied in detail. All the results indicate that Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ phosphors have potential applications as near UV-convertible phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of novel luminescent phosphors Sr 10 (PO 4 ) 6 O:Eu 2+ with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr 9.97 (PO 4 ) 6 O:0.03Eu 2+ phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu 2+ in Sr 10 (PO 4 ) 6 O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr 10 (PO 4 ) 6 O:Eu 2+ phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr 10 (PO 4 ) 6 O:Eu 2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. [ABSTRACT FROM AUTHOR]

The Ca 9 La(PO 4 ) 5 (SiO 4 )Cl 2 :Dy 3+ (CLPSCl:Dy 3+ ) powder phosphor with apatite structure has been successfully synthesized via high-temperature solid state method. Single phase in such phosphor was verified through X-ray diffraction (XRD) technique. The Dy ions concentration dependent luminescence properties including emission, excitation and lifetimes of Dy ions were characterized using photoluminescence (PL) spectroscopy. The results showed that CLPSCl:Dy 3+ phosphor could efficiently assimilate the n -UV light and emit blue (~486 nm) and yellow light (~578 nm), originating from the f-f transitions of Dy 3+ . The critical Dy 3+ quenching concentration (QC) was determined to be about 12 mol%. The concentration quenching mechanism was also determined to be dipole–dipole interaction. [ABSTRACT FROM AUTHOR]

A series of Eu 2+ and Eu 2+ /Tb 3+ co-doped Ba 3 GdNa(PO 4 ) 3 F phosphors have been synthesized via a high temperature solid-state reaction. The relative intensity of PL spectra of Ba 3 GdNa(PO 4 ) 3 F: x Eu 2+ increases with increasing x value, and reaches a maximum at x =0.04. Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ phosphors exhibit a broad excitation band ranging from 220 to 450 nm, which matches perfectly with the characteristic emission of n -UV light-emitting diode (LED) chips. Upon 365 nm excitation, the Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ phosphors show two dominating bands peaked at 466 and 543 nm, which are assigned to the 4f 7 →4f 6 5d 1 transition of the Eu 2+ ions and the 5 D 4 → 7 F 5 transition of the Tb 3+ ions, respectively. In view of the energy transfer mechanism between Eu 2+ and Tb 3+ , the Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ emission color can adjust from blue to green, and their chromatic coordinates ( x , y ) vary from (0.16, 0.135) to (0.254, 0.398). The critical distance was also calculated to be 16.90 Å. The above results indicate that the Ba 3 GdNa(PO 4 ) 3 F: Eu 2+ , Tb 3+ phosphors are a candidate for blue–green components in the application of n -UV w -LEDs. [ABSTRACT FROM AUTHOR]