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Orange–red-emitting phosphors Ca9La(VO4)7:Sm3+ and Ca9La(VO4)7:Sm3+,M+ (M+ = Li+, Na+, and K+) were synthesized by the combustion method. Their crystal structure, microstructure, luminescence properties, and decay performance were investigated in detail. The results revealed that the as-prepared samples were crystallized in a trigonal structure (space group of R3c, No. 161). Under 405-nm excitation, the Ca9La(VO4)7:Sm3+ phosphor exhibited excellent orange–red emission. The Sm3+ ions were quenched at 0.02 equivalents by electric dipole–dipole interactions. After the introduction of alkali metal ions Li+, Na+, and K+, the luminescence properties of the Ca9La(VO4)7:Sm3+ samples were noticeably enhanced, particularly those of that co-doped with Li+. The chromaticity coordinates of Ca9La(VO4)7:0.02Sm3+, 0.02Li+ and Ca9La(VO4)7:0.02Sm3+ were (0.610, 0.390) and (0.604, 0.395), respectively, close to those of the commercial red phosphor Y2O2S:Eu3+ (0.622, 0.351). The results suggested that the Ca9La(VO4)7:0.02Sm3+, 0.02Li+ phosphor may serve as an orange–red emitter for applications in white light-emitting diodes excited by near-ultraviolet radiation. [ABSTRACT FROM AUTHOR]

Dy3+-doped and Dy3+/Eu3+ co-doped NaBi(MoO4)2 phosphors were successfully synthesized using a high temperature solid-state method. The crystal structure and phase purity of these as-prepared samples were characterized by X-ray diffraction. Under 453 nm excitation, NaBi(MoO4)2:Dy3+ phosphors exhibited the characteristic weak blue emission peak at 488 nm and strong yellow emission peak at 577 nm, which originate from the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. Therefore, a white light could be composed of a blue light from chip and yellow emission of NaBi(MoO4)2:Dy3+ phosphor. Additionally, color-tunable emissions were observed in the spectra of NaBi(MoO4)2:Dy3+, Eu3+ phosphors due to efficient energy transfer from Dy3+ to Eu3+ ions. By varying co-doping concentrations of Dy3+ and Eu3+ ions, the emission color of NaBi(MoO4)2:Dy3+, Eu3+ could be varied for high quality blue-excited white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Dysprosium doped chlorapatite, Ca5(PO4)3Cl:Dy3+ white-emitting phosphors were synthesized by a solid-state reaction method. The effects of synthesis temperature, Dy3+ doping concentration, Eu3+ co-doping concentration and charge compensator Li+ co-doping on the crystal structures and luminescence properties of Ca5(PO4)3Cl:Dy3+ samples were investigated. Ca5(PO4)3Cl:Dy3+, Eu3+ and Ca5(PO4)3Cl:Dy3+, Li+ phosphors with standard Ca5(PO4)3Cl structure were prepared by heating above 900 °C, and the doped Dy3+, Eu3+/Li+ ions had no effect on the crystal structure. Under ultraviolet excitation at 366 nm, the emission spectra of Ca5(PO4)3Cl:Dy3+ phosphors exhibited two characteristic peaks of Dy3+ at 484 and 577 nm, which corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 electron transitions, respectively. Both blue and yellow emissions within a single-component host would constitute the white light. The white emission intensity of Ca5(PO4)3Cl:Dy3+ was enhanced markedly by Li+ co-doping as charge compensator. Moreover, Eu3+ co-doped Ca5(PO4)3Cl:Dy3+ phosphor showed an excellent warm white light with high chromaticity coordinates and low correlated color temperature though an additional red emission of Eu3+. The results indicate that these Ca5(PO4)3Cl:Dy3+, Eu3+/Li+ phosphors have potential applications in the field of white light-emitting diodes as single-component white-emitting phosphors. [ABSTRACT FROM AUTHOR]

The stability of phosphors and matrix under humid conditions and elevated temperatures is essential for the stable performance of light-emitting diodes. We synthesized a series of NaYSiO 4 : x Eu3+ (x = 0.00–0.14) phosphors via a sol-gel reaction. The NaYSiO 4 crystallizes in a hexagonal structure (space group P63/m) with a bandgap value of 4.60 eV. In this lattice, doped Eu3+ occupied the center of non-inversion symmetry. Under the optimal 394 nm excitation, the NaYSiO 4 :0.04Eu3+ sample showed a strong red emission at 618 nm with a high color purity of up to 94.98 %. Impressively, it exhibited high thermal stability (523 K, > 50 %, ∆ E = 0.24089 eV) and moisture resistance. Due to the protection of the stable coordination environment provided by cyclic Si-O-Si bands and strong binding energy, it retained 90.2 % of its original intensity after exposure under the relative humidity of 85 % at 85 °C for 240 h. Furthermore, this red phosphor was packaged into a cold white light-emitting diode with Commission International de l′Eclairage (0.3250, 0.3364). From the perspective of host lattice structure, this work provides a new strategy to withstand luminous degradation under humid and warm conditions. • NaYSiO 4 :Eu3+ exhibits excellent moisture resistance and thermal stability. • NaYSiO 4 :Eu3+ is an effective red-emitting component with high color purity. • Eu3+ occupies non-inversion symmetry sites protected by Si-O-Si bands. [ABSTRACT FROM AUTHOR]

To improve the luminescence property of Sm3+ in Y 2 Mo 3 O 12 , partial Ca2+-F- co-substituted Y 2 Mo 3 O 12 :Sm3+ phosphor, namely Y 2- x Ca x Mo 3 O 12- x F x :Sm3+, was prepared using a solid-state method. The effect of introducing Ca2+-F- ion pairs on structure and luminescence properties of Y 2 Mo 3 O 12 :Sm3+ was studied in depth. XRD patterns not only manifested that all as-prepared Y 2- x Ca x Mo 3 O 12- x F x :Sm3+ samples had standard Y 2 Mo 3 O 12 structure, but also indicated the introduction of Ca2+-F- ion pairs did not cause the change of crystal structure. Under the near ultraviolet excitation of 404 nm, the emission peaks of Y 2 Mo 3 O 12 :Sm3+ were located at 567 nm, 605 nm and 652 nm, respectively, resulting from the 4f→4f electron transitions of Sm3+ ions. Furthermore, the luminescence intensity of Sm3+ was obviously enhanced through the co-substitution of Y3+-O2- ions with Ca2+-F- ions in Y 2 Mo 3 O 12 structure, and the chromaticity coordinates moved towards red region, which due to the environmental effect of crystal field around Sm3+. Besides, the red LED device was manufactured for suitable chromaticity parameters. All results indicated that the as-prepared Y 1.84 Ca 0.06 Mo 3 O 11.94 F 0.06 :0.10Sm3+ red-emitting phosphor could become a promising candidate for application of white light-emitting diodes and plant illumination. [ABSTRACT FROM AUTHOR]

A series of β -Ca 3 (PO 4) 2 type single-component Ca 19 Zn 2 (PO 4) 14 :Dy3+, M+ (M = Li, Na and K) white-emitting phosphors were synthesized via a high-temperature solid-state reaction method, where alkali metal ions (M+) co-doped as charge compensator into the Ca 19 Zn 2 (PO 4) 14 :Dy3+ phosphor was aimed at improving the overall luminescence. The influences of synthesis temperature and the M+ introduction on both structure and luminescence property were thoroughly studied. X-ray diffraction patterns verify that the as-prepared phosphors attain the standard Ca 19 Zn 2 (PO 4) 14 phase without impurities. Photoluminescence peaks at 484 nm and 575 nm (originating from the 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 electron transitions of Dy3+ ions) were produced for all samples with an excitation of 386 nm, which then combined to emit white light. The luminescence intensities of Ca 19 Zn 2 (PO 4) 14 :Dy3+ were dramatically improved through co-doping with M+ into the phosphor structure. These results demonstrate the promising application prospects of Ca 19 Zn 2 (PO 4) 14 :Dy3+, M+ white-emitting phosphors in white light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of Cd 2 V 2 O 7 :Eu 3+ , Li + red phosphors was prepared by a solid-state reaction method. A pure Cd 2 V 2 O 7 phase with monoclinic structure was obtained by heating to a temperature range of 600–850 °C. The effects of Eu 3+ doping and Li + co-doping concentrations on the luminescence properties of Cd 2 V 2 O 7 :Eu 3+ , Li + samples were investigated. Under excitation at 375 nm, the as-prepared Cd 2 V 2 O 7 :Eu 3+ phosphors exhibit a red emission peak at 618 nm due to the 5 D 0 → 7 F 2 electronic transition of Eu 3+ . The luminescence properties of Cd 2 V 2 O 7 :Eu 3+ , Li + samples are improved significantly by the addition of Li + as charge compensator compared to the Cd 2 V 2 O 7 :Eu 3+ phosphor. The results indicate that Cd 2 V 2 O 7 :Eu 3+ , Li + phosphor could be a promising red phosphor in near ultraviolet-excited white light-emitting diodes for warm white light. [ABSTRACT FROM AUTHOR]