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Series of white light-emitting NaSrPO4:Dy3+ phosphors were synthesized via a sol–gel method. Small amounts of Sm3+ ions were co-doped into the phosphors to enhance their luminescence. The effects of Dy3+/Sm3+ co-doping concentrations and synthesis temperature on the phosphors' structures and luminescence properties were investigated. The results of X-ray diffraction confirmed that the characteristic diffraction peaks of the phosphors were in accord with those of the standard NaSrPO4 structure. Energy dispersive spectroscopy indicated that the NaSrPO4:Dy3+ samples were prepared with stoichiometric ratios of elements. Under ultraviolet light excitation of 348 nm, the NaSrPO4:Dy3+ phosphors emitted a white light which was composed of two emission peaks at 484 nm (blue) and 577 nm (yellow) corresponding to the magnetic dipole transition 4F9/2 → 6H15/2 and electronic dipole transition 4F9/2 → 6H13/2 of Dy3+ ions, respectively. Based on Sm3+ co-doping, a characteristic red emission at 602 nm arose and a warm-white light containing a lower CCT value was obtained. Besides, the luminescence lifetime of Dy3+ decreased while that of Sm3+ increased as dosages of Sm3+ were added, indicating efficient energy transfer from Dy3+ to Sm3+ happened. Therefore, NaSrPO4:Dy3+, Sm3+ phosphors are promising candidates for application in warm-white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Eu3+ activated red phosphors based on the CaY x (MoO 4) 1.5x+1 (x = 0.2, 0.4, 0.6, 1, 2) as host materials were synthesized by using a combustion method. XRD analysis demonstrated that the synthesized samples matched with the standard card CaMoO 4 (JCPDS NO.77-2239) belonging to the tetragonal of the I4 1 /a space group. All samples showed several narrow sharp emission peaks under 393 nm n-UV excitation, the strongest of which was at 618 nm attributed to the 5D 0 →7F 2 transition of Eu3+. The optimal composition of the host was found to be CaY 0.6 (MoO 4) 1.9 (hereafter referred to as CYMO). After doping Sm3+ into CYMO:Eu3+ phosphor, the absorption peaks of Eu3+ at 393 and 464 nm were broadened, and the peak intensity was also significantly higher than that of single-doped Eu3+. The energy transfer phenomenon between Sm3+ and Eu3+ was discovered by the excitation and emission spectra in CYMO:Eu3+,Sm3+ phosphors, and verified by the fluorescence lifetime of Sm3+ ions in the phosphors. The energy transfer mechanism between Sm3+ and Eu3+ is a dipole-dipole interaction, where the energy transfer efficiency in CYMO phosphor doped with 13% Eu3+ and 3% Sm3+ is 17.9%. The CIE coordinate and color purity were calculated as (x = 0.6598, y = 0.3388) and 93.72%, which indicated that the CYMO:13%Eu3+,3%Sm3+ phosphor is a red phosphor with excellent performance for potential application in n-UV light excited w-LEDs. [ABSTRACT FROM AUTHOR]

A series of Y2Mo4O15:Pr3+, Tb3+ red-emitting phosphors is synthesized via a solid-state reaction. The X-ray diffraction results indicate that the patterns of Y2Mo4O15:Pr3+, Tb3+ samples match well with the standard Y2Mo4O15 monoclinic structure. Under blue excitation at 453 nm, the Y2Mo4O15:Pr3+ phosphors show a red emission peaked at 614 nm, corresponding to the characteristic 1D2 → 3H4 electronic transition of Pr3+. Under near-ultraviolet excitation at 375 nm, the Y2Mo4O15:Tb3+ phosphor results in a double emission at 552 nm and 490 nm, which corresponding to the 5D4 → 7F5 and 5D4 → 7F6 electronic transitions of Tb3+. Furthermore, the luminescence properties of Y2Mo4O15:Pr3+ phosphor, especially luminescence intensity, was observably improved by the Tb3+ co-doping, which due to the emission peak of Tb3+ matches well with the excitation peak of Pr3+ at 490 nm and the resulted energy transfer between Tb3+ and Pr3+. The chromaticity coordinates of Y2Mo4O15:Pr3+, Tb3+ phosphors are all located in the red region. The results indicate that the prepared Y2Mo4O15:Pr3+, Tb3+ red phosphors are suitable for the applications of blue-excited warm 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]

In this study, a series of white light-emitting NaSrVO 4 :Dy3+ phosphors with La3+ co-doping were produced by a combustion method. The configurations of the as-prepared NaSrVO 4 :Dy3+ and NaSrVO 4 :Dy3+, La3+ specimens are consistent with the standard phase of NaSrVO 4. The impacts of the Dy3+ concentration and La3+ co-doping on the luminescence characteristics of NaSrVO 4 : Dy3+ phosphors were explored. The specimens excited by near-ultraviolet light displayed emission peaks at 580 (yellow) and 484 nm (blue), which were ascribed to the 4F 9/2 → 6H 13/2 and 4F 9/2 → 6H 15/2 transitions of the Dy3+ ions, respectively. The white light was manufactured by these two emissions from the NaSrVO 4 : Dy3+ phosphor. Photoluminescence studies demonstrated that the La3+ co-doping efficiently improved the luminescence characteristics of the NaSrVO 4 : Dy3+ phosphor. These results suggest that the NaSr 0.9425 VO 4 : 0.05Dy3+, 0.0075La3+ phosphors excited by near-ultraviolet are promising materials for white light-emitting diodes. [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 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]

A novel white emitting phosphate-based phosphor Ca 3- x Li x (PO 4) 2- x (SO 4) x :Dy3+, Sm3+ with high emission intensity and lower correlated color temperature were successfully synthesized via the sol-gel method. The structures of these prepared phosphors matched well with standard Ca 3 (PO 4) 2. The Dy3+-doped Ca 3- x Li x (PO 4) 2- x (SO 4) x phosphors showed white luminescence via the combination of blue (487 nm) and yellow (578 nm) emissions, which were attributed to the 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 electron transitions of Dy3+, respectively. The synthesized phosphor exhibited a significant enhancement in luminescence intensity at the optimum value of x = 0.15. With the incorporation of Sm3+, a warm white emission with lower correlated color temperature (4281 K) was achieved in Dy3+/Sm3+ co-doped samples. The obtained external quantum efficiency reached 21.7% in the optimized phosphor. The improved performance was strongly associated with red emission supplemented by Sm3+, and it demonstrated the existence of efficient energy transfer between the Dy3+ and Sm3+ ions (4F 9/2 → 4G 7/2 and 4F 9/2 → 4G 5/2). Overall, the investigation carried out by us has revealed that the luminescence properties of Ca 3 (PO 4) 2 phosphor can be significantly improved through Li+/S6+ partial substitution and Dy3+/Sm3+ co-doping. Image 1 • A novel Li+/S6+ co-substituted Ca 3 (PO 4) 2 :Dy3+ white-emitting phosphor was prepared. • Ca2+/P5+ couples were partially substituted with Li+/S6+ for luminescence enhancement. • A white light could be realized with a blue emission and yellow emission of Ca 3- x Li x (PO 4) 2- x (SO 4) x :Dy3+. • Warm white emission with low CCT can be achieved for Ca 2 · 85 Li 0 · 15 (PO 4) 1 · 85 (SO 4) 0.15 :Dy3+ phosphor by Sm3+ ions co-doping. [ABSTRACT FROM AUTHOR]