White light-emitting diodes (WLEDs) with high luminous brightness, low energy consumption, long lifetime and environmental friendliness can be applied in various fields. In order to improve the quality of white light, red phosphors are necessary.

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Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu 3+ -doped Ba 6 Gd 2 Ti 4 O 17 phosphor seems to be an exception. In the series of Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ (x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba 6 Gd 2 Ti 4 O 17 , directly increasing the number of Eu 3+ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu 3+ -doped Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ (x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l'Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up to 94.4%. Moreover, warm white light with the CIE chromaticity coordinates of (0.39, 0.39), the correlated color temperature of 3756 K, and the color rendering index of 82.2 is successfully generated by fabricating this highly Eu 3+ -doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb 3+ and blue BAM:Eu 2+ phosphors. KEYWORDS: Eu 3+ -doped phosphor, Ba 6 Gd 2 Ti 4 O 17 host, nonconcentration quenching, energy migration, light-emitting diodes

Series of NaLa(PO 3 ) 4 :Tb 3+ /Eu 3+ phosphors were prepared by a hightemperature solid-state reaction technique. Structure refinements were performed based on powder X-ray diffraction (XRD) data. VUV−UV−vis photoluminescence (PL), fluorescence decays, time-resolved emission spectra (TRES), and low-voltage cathodoluminescence (CL) spectra were utilized to investigate the luminescence and energy transfer processes. Under VUV−UV light and low-voltage electron beam excitation, NaLa(PO 3 ) 4 :Tb 3+ and NaLa(PO 3 ) 4 :Eu 3+ exhibit characteristic emissions of Tb 3+ ( 5 D 4 → 7 F J ) and Eu 3+ ( 5 D 0 → 7 F J ), respectively. By adjusting the doping concentration of Eu 3+ ions in NaTb 0.70 La (0.30-x) Eu x (PO 3 ) 4 , tunable emission colors are realized in a large color gamut, in which energy transfer from Tb 3+ to Eu 3+ was observed and discussed in detail. On the basis of the good VUV−vis PL and CL properties, NaLa(PO 3 ) 4 :Tb 3+ /Eu 3+ phosphors might be promising for applications in plasma display panels (PDPs) and field emission displays (FEDs).

In this work, we report a new and efficient red phosphor BaGeF 6 :Mn 4+ (denoted as BGFM) by hydrothermally etching BaCO 3 and GeO 2 in HF solution with an optimized KMnO 4 concentration. The crystal structure and morphology were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) in details. The influence of synthesis conditions on its photoluminescent (PL) properties has been investigated comprehensively. It can present a broad adsorption and sharp emissions in blue and red ranges respectively. The white LED device made of blue GaN chip merged with YAG:Ce-BGFM mixture presents warmer white light than that merged with only one YAG:Ce component.