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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]

In this work, we fabricated NiFe2O4/C composite with a coral-like structure through co-precipitation approach followed by thermal decomposition. The composite with a large surface area of 162.1 m2 g−1 and an average pore size of 11.8 nm was obtained. The porous structure in the composite derived from oxalate can effectively accommodate the volume changes of NiFe2O4 during the cycling processes. When used as anode materials, the initial charge and discharge capacities of the composite were 926.7 and 1277.7 mAh g−1 at 100 mA g−1. After 50 cycles, the reversible capacity of NiFe2O4/C could still remain at 892.4 mAh g−1. Even at a current density of 2000 mA g−1, the reversible capacity still reached 523.3 mAh g−1. The results showed that the synergy between NiFe2O4 and carbon improved the electrochemical performance, and the porous composite could stabilize the structure of the electrode. [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]

In the study, a new kind of tetrad cathode lithium-ion battery material (LiNi0.6Co0.2-xMn0.2VxO2 (x = 0, 0.06, 0.08, 0.10)) was synthesized and then characterized by XRD, XPS, SEM, EDS, electrochemical measurements, CV, and EIS. The homogenous distribution of vanadium element on the materials was verified and the layer crystal structure was not changed when x = 0.08. XPS results indicated that suitable vanadium substitution reduced cation mixing on the surface due to the lower content of Ni2+. Electrochemical measurements confirmed that LiNi0.6Co0.12Mn0.2V0.08O2 had the highest initial coulombic efficiency (80 % at 0.05 C), rate capacity (129.4 mAh/g at 5 C), and cycling performance (92.6% at 1 C) at the cutoff voltage of 4.6 V, which were much better than those of LiNi0.6Co0.2Mn0.2O2. LiNi0.6Co0.12Mn0.2V0.08O2 showed good dynamic properties in CV and EIS tests. The results of XRD and SEM for cycled electrodes showed that the introduction of vanadium could significantly relieve structural damages of LiNi0.6Co0.2Mn0.2O2 during charge/discharge processes. This study indicated that controlled vanadium introduction could effectively improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 for developing the high-voltage cathodes for high-energy lithium-ion batteries. [ABSTRACT FROM AUTHOR]

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]