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Self-activated Ca 5 Mg 3 Zn(VO 4 ) 6 and Ca 5 Mg 3 Zn(VO 4 ) 6 :xEu 3+ phosphors were synthesized via a high-temperature solid-state reaction route. The crystalline structure and luminescence properties of the phosphors were analyzed using an X-ray diffractometer and a photoluminescence spectrometer. The explored results indicated that by varying calcination temperature and the raw material ratio of Ca 2+ /Mg 2+ /Zn 2+ , the phosphors could be developed with different phases, crystallinity, and various fluorescence performances. The fluorescence spectrum of Ca 5 Mg 3 Zn(VO 4 ) 6 showed a broad emission band over the range 400-650 nm under an excitation wavelength of 330 nm, as well as green light emission. Furthermore, after introduction of Eu 3+ ions in Eu(VO 4 ) 4 , the luminescence intensity of the Eu 3+ ions greatly increased as the Eu 3+ ion concentration increased at the 393 nm excitation wavelength, showing green-yellow light emission simultaneously. Therefore, the obtained phosphors could be used as a potential green-yellow-emitting luminescent material in a white light-emitting diode device., (© 2020 John Wiley & Sons, Ltd.)

Sr 3 (PO 4 ) 2 :Dy 3+ ,Li + phosphors were prepared using a simple high temperature solid method for luminescence enhancement. The structures of the as-prepared samples agreed well with the standard phase of Sr 3 (PO 4 ) 2 , even when Dy 3+ and Li + were introduced. Under ultraviolet excitation at 350 nm, the Sr 3 (PO 4 ) 2 :Dy 3+ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the 4 F 9/2  →  6 H 15/2 and 4 F 9/2  →  6 H 13/2 transitions of Dy 3+ ions, respectively. A white light was fabricated using these two emissions from the Sr 3 (PO 4 ) 2 :Dy 3+ phosphors. The luminescence properties of Sr 3 (PO 4 ) 2 :Dy 3+ ,Li + phosphors, including emission intensity and decay time, were improved remarkably with the addition of Li + as the charge compensator, which would promote their application in near-ultraviolet excited white-light-emitting diodes., (Copyright © 2017 John Wiley & Sons, Ltd.)

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]

Luminescent perovskite photocatalysts activated by Pr3+ were prepared by combustion. The structural phase, morphology, and chemical composition of the as-prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy. The photocatalytic activities of the synthesized samples were investigated on the basis of the degradation of methylene blue (MB) under UV light irradiation. CaTiO3:Pr3+ was obtained in high purity and good crystallinity with a perovskite structure. The degradation of the photocatalyst was fitted with pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Compared to CaTiO3:Pr3+, Ca1–xTiO3:Pr3+ (x = 0–0.3) multifunctional materials exhibit higher luminescence intensity and photocatalytic activity toward the degradation of MB. Ca0.8TiO3:0.1%Pr3+ exhibited the best performance. [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]

Eu3+-doped calcium titanate red phosphors, Ca1-xZnxTiO3:Eu3+, were prepared by the sol-gel method. The structure of prepared Ca1-xZnxTiO3:Eu3+ phosphors were investigated by X-ray diffraction and infrared spectra. Due to the 5D0 → 7F1-3 electron transitions of Eu3+ ions, photoluminescence spectra showed a red emission at about 619 nm under excitation of 397 nm and 465 nm, respectively. When zinc was added to the host, the luminescent intensity of Ca1-xZnxTiO3:Eu3+ was markedly improved several fold compared with that of CaTiO3:Eu3+. Ca0.9Zn0.1TiO3:Eu3+ also had higher luminescence intensity than the commercially available Y2O3:Eu3+ phosphors under UV light excitation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Via wet chemical method with organic assistant, ZnS:Cu/ZnS core/shell structure was prepared. X-ray diffraction measurements showed that ZnS:Cu was formed with zinc blende structure, and ZnS shell growth on the surface was indicated through a red-shift in the UV-Vis absorption spectra with increasing particle size. The emission peak at about 510 nm was observed, which should be assigned to recombination of an electron from the shallow delocalized donor levels at thet2level of Cu2+centers. As passivation layer, effect of ZnS shell on luminescence intensity and lifetime of ZnS:Cu were investigated. Comparing with uncoated ZnS:Cu, ZnS shell really enhanced the luminescence intensity and lifetime significantly, which resulted from the reduction of nonradiative recombination sites. [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 series of single-phase color-turning CaZrO 3 : Ln (Ln = Tb3+, Eu3+, Tb3+/Eu3+) phosphors was synthesized through citric acid-fueled combustion method. The as-prepared samples had the perovskite structure with Pnma space group and elements uniformly distributed in nanosized particles. CaZrO 3 : Eu3+ phosphor produced red luminescence due to the 5D 0 →7F 2 transition at 619 nm CaZrO 3 : Tb3+ phosphor produced green and blue luminescence due to the 5D 4 →7F 6, 5 transition at 487 nm and 548 nm. Under UV irradiation at 254 nm, the CaZrO 3 : Ln (Ln = Tb3+, Eu3+, Tb3+/Eu3+) phosphors achieved tunable full-color emission in a wide range from blue to green, warm white, and red. The corresponding CIE coordinates were (0.2546, 0.2413), (0.3196, 0.5085), (0.3603, 0.3896) and (0.6089, 0.3844). The energy transfer from ZrO 3 2− to Tb3+ and then to Eu3+ was determined by the dipole-dipole mechanism in CaZrO 3 : 0.03 Tb3+, xEu3+ phosphors. The excellent temperature stability of CaZrO 3 : 0.03 Tb3+, 0.01Eu3+ phosphor (ΔE = 0.2659 eV) indicates that CaZrO 3 : Ln (Ln = Tb3+, Eu3+, Tb3+/Eu3+) phosphors have broad application prospects in W-LED devices. • A lower temperature fast method (900 °C) was used to synthesize RE-doped CaZrO 3 phosphors. • Full-color-emitting from blue to green, warm white and red single-phase CaZrO 3 : Ln phosphors. • Recognition of the energy transfer mechanism between ZrO 3 2−, Eu3+ and Tb3+. [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]

A series of Ca(Ti 1− x Zr x)O 3 :Dy3+ phosphors were fabricated using a combustion method. The lattice structure, morphological features, and luminescence performances of the specimens were obtained. Rietveld refinement of the XRD patterns confirmed the crystal distortion of CaTiO 3 after Zr4+codoping and the positional occupation of Zr4+ in the CaTiO 3 crystal lattice. The photoluminescence spectroscopy results indicated that the fluorescence emission intensity of CaTiO 3 :Dy3+ was substantially enhanced by Zr4+ codoping and that the optimum doping concentration of Zr4+ was 40% mol. The quantum yield of the Ca(Ti 0·6 Zr 0.4)O 3 :Dy3+ phosphor was measured to be 9.9%, and its fluorescence lifetime decreased with the increasing concentration of Zr4+ doping. Furthermore, the lowest color temperature was observed for Ca(Ti 0·6 Zr 0.4)O 3 :Dy3+ among the investigated phosphors and its color coordinate was the closest to the standard white-light color coordinate. These results suggest that the Ca(Ti 0·6 Zr 0.4)O 3 :Dy3+ phosphor excited by near-ultraviolet light is a potential material for application in white light-emitting diodes. • The lattice parameters changes after incorporation of Zr4+ into CaTiO 3 :Dy3+. • The XRD structural refinement certificated the rationalization of Zr4+ substitute Ti4+ in CaTiO 3 :Dy3+ structure. • The fluorescence properties enhanced after Zr4+ doping. [ABSTRACT FROM AUTHOR]