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Preparation and Enhancement of Luminescent Intensity of New Rare Earth Molybdate NaLa(MoO4)2:Eu3+ Phosphors
摘要： Novel red-emitting rare earth molybdate phosphors NaLa(MoO4)2:Eu3+ have been successfully synthesized by sol-gel method assisted by microwave. The as-synthesized samples were characterized by means of Fourier transform infrared spectroscopy, X-ray diffraction and Fluorescence spectrophotometer, respectively. The results show that the target product NaLa(MoO4)2:Eu3+ have been synthesized by calcining precursor at 800 oC. The obtained samples belong to tetragonal Scheelite-structure and I41/a space group. The excitation spectrum of NaLa(MoO4)2:Eu3+ has a broad band in the range of 250-350 nm and the main peak is at 301 nm. The broad band can be ascribed to the charge transfer band of Mo-O and Eu-O. The sharp lines in 350-500 nm range are due to 4f-4f transitions of Eu3+. The emission spectrum contains a series of narrow peaks, with the main peak at 616 nm originated from the electric dipole transition of 5D0 → 7F2 of Eu3+. The appropriate doping amount of Bi3+ and flux NH4F can enhance luminescent intensity of the sample effectively.
关键词： Rare earth molybdate,Sol-gel method assisted by microwave,Red-emitting phosphors,NaLa(MoO4)2:Eu3+
更新于2025-09-23 15:23:52
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Novel highly luminescent double-perovskite Ca2GdSbO6:Eu3+ red phosphors with high color purity for white LEDs: Synthesis, crystal structure, and photoluminescence properties
摘要： High-efficiency red-emitting phosphors are required to fabricate high-performance white light-emitting diodes (LEDs). Herein, the novel highly efficient Eu3+-activated Ca2GdSbO6 double-perovskite red phosphors with good thermal stability toward warm-white LEDs were reported. A series of Ca2Gd(1-x)EuxSbO6 red phosphors with different Eu3+ doping concentrations (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by using high-temperature solid-state reaction method. Under the excitation of 396 nm near-ultraviolet light, these Ca2Gd(1-x)EuxSbO6 phosphors showed intense red emissions peaking at 612 nm due to the 5D0→7F2 transition of Eu3+ ions. The strongest luminescence intensity reached when Eu3+ doping concentration was x = 0.5, and the critical distance between Eu3+ activators was calculated to be 7.97 ?. The concentration quenching mechanism was due to the dipole-dipole interaction of Eu3+ ions. The CIE color coordinates of the optimal Ca2Gd0.5Eu0.5SbO6 phosphors were determined to be (0.6629, 0.3367), and the corresponding color purity reached about 94.9%. Importantly, the Ca2Gd0.5Eu0.5SbO6 phosphors revealed outstanding internal quantum efficiency of 73% and good thermal stability. The emission intensity of Ca2Gd0.5Eu0.5SbO6 phosphors at 423 K still remained about 73% of its initial value at 303 K. Finally, a prototype white LED device was fabricated by coating the phosphor blend of commercial blue-emitting BaMgAl10O17:Eu2+ and our as-prepared red-emitting Ca2Gd0.5Eu0.5SbO6 on a 395 nm LED chip. Under 20 mA driven current, the device showed bright warm-white light with CIE color coordinates of (0.3888, 0.3943), correlated color temperature of 3911 K, and color rendering index of 88.4. The results demonstrated that the developed novel red-emitting Ca2Gd0.5Eu0.5SbO6 phosphors could be used as potential color converters in white LEDs.
关键词： White LEDs,Photoluminescence,Ca2GdSbO6,Double-perovskite,Eu3+ ions,Red-emitting phosphors
更新于2025-09-23 15:19:57
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Novel red emitting LnTaO4: Eu3+ (Ln = La, Y) phosphors for warm white LEDs
摘要： LnTaO4: Eu3t (Ln ? La, Y) phosphors were synthesized by high-temperature solid-state reaction. Powder X-ray diffraction analysis confirmed the pure phase formation. Diffuse reflection spectra, excitation and emission spectra, the CIE chromaticity coordinates as well as the temperature-dependent emission spectra were investigated those phosphors. Upon near UV and blue excitation LnTaO4: Eu3t (Ln ? La, Y) show intense red emission of Eu3t. The optimum concentration of Eu3t in LaTa1-xEuxO4 phosphor was x ? 0.20, and concentration quenching mechanism was the electric dipole-dipole interaction. Furthermore, the critical transfer distance was obtained and the CIE chromaticity coordinates of LaTaO4: Eu3t samples were close to the National Television System Committee standard values. The temperature-dependent luminescence indicated LaTaO4: Eu3t exhibited moderate thermal stability. Those results suggested that LnTaO4: Eu3t (Ln ? La, Y) as red emitting phosphors could be potential candidates for white LEDs.
关键词： Luminescent properties,Red emitting phosphors,White LED,Thermal stability
更新于2025-09-23 15:19:57
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Synthesis and photoluminescence properties of a new blue-light-excitable red phosphor Ca2LaTaO6:Eu3+ for white LEDs
摘要： In this paper, a series of Eu3+-activated double-perovskite Ca2LaTaO6 (abbreviated as CLT:xEu3+; x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) red-emitting phosphors have been successfully synthesized via the conventional high-temperature solid-state reaction method. These samples were characterized by X-ray diffraction, Rietveld refinement, field-emission scanning electron microscope, elemental mapping, energy-dispersive spectrum, room-temperature photoluminescence, decay lifetimes, quantum efficiency, CIE color coordinates, and temperature-dependent emission spectra. Interestingly, under blue excitation into the 7F0→5D2 transition of Eu3+ at 466 nm, the CLT:xEu3+ phosphors could emit bright red light corresponding to the 5D0→7FJ (J = 1, 2, 3, 4) transitions. Their luminescence properties have been investigated as a function of the Eu3+ ions concentration. It was found that the CLT:0.4Eu3+ sample exhibited the strongest emission intensity, and the concentration quenching effect was caused by the dipole-dipole interaction among Eu3+ activators. Impressively, the emission intensity of the as-prepared CLT:0.4Eu3+ phosphors was about 4.3 times higher than the commercial Y2O3:Eu3+ red phosphors. Moreover, the CLT:0.4Eu3+ sample had excellent CIE color coordinates of (0.665, 0.334) and supereminent color purity of 95.3%. Notably, the study on temperature-dependent emission spectra of the CLT:0.4Eu3+ sample revealed its good thermal stability and color stability at high temperatures. These excellent photoluminescence properties of CLT:0.4Eu3+ phosphors indicated their promising application potential in white light-emitting diodes as blue-light-excitable red phosphors.
关键词： Ca2LaTaO6,White LEDs,Red-emitting phosphors,Eu3+ ions,Double-perovskite,Photoluminescence
更新于2025-09-23 15:19:57
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Photoluminescence Tuning in Novel Bi3+/Mn4+ Co-doped La2ATiO6:(A = Mg, Zn) Double Perovskite Structure: Phase Transition and Energy Transfer
摘要： Red-emitting phosphors are indispensable componans to achieve warm white light of phosphor-converted white light emitting diodes (pc-WLEDs). However, the luminous efficiency and stability for red phosphors are still a big challenge. In this work, we develop red-emitting double perovskite phosphors La2ATiO6:Bi3+, Mn4+ (A = Mg, Zn) (LAT: Bi3+, Mn4+) and disscuss the relationship between double perovskite phosphors structure and luminescence performance in detail. By designing Mg2+/Zn2+ cation substitution, It is noteworthy that the internal quantum efficiency (IQE) is remarkeblely enhanced beyond 20%. According to Rietveld refinement results for La2Mg(1-w)ZnwTiO6:Bi3+, Mn4+ (0 ≤ w ≤ 1) (LM(1-w)ZwT:Bi3+, Mn4+) solid solution, the proposed machanism of the spectral adjustment is ascribed to the appearance of phase transition, which results in a lower local structure symmetry of [LaO12] polyhedron and variation of crystal field environment for Mn4+. Notably, it is the first time to reveal the influence of local structure variation on luminescence tuning in double perovskite structure phosphors, which could offer a guidance to develop new phosphors system. In addition, we firstly succeed in realizing Bi3+/Mn4+ co-doped energy transfer in double perovskite structure phosphors. Due to the Bi3+→Mn4+energy transfer in LAT, red emission of Mn4+ ions could be dramatically enhanced. The energy transfer efficiency of LAT: Bi3+, Mn4+ eventually reaches exceed 90%. The IQE and thermal stability are all enhanced around 30% than non-codoped samples, respectively. These results indicate that Bi3+→Mn4+energy transfer strategy could play a pivotal role in developing highly efficient red-emitting phosphor. The performance of the fabricated pc-WLEDs devices indicates that LAT:Bi3+, Mn4+ could be a promising red phosphor for near ultraviolet (n-UV) based on warm pc-WLEDs.
关键词： pc-WLEDs,Bi3+/Mn4+ co-doped,double perovskite phosphors,energy transfer,Red-emitting phosphors
更新于2025-09-10 09:29:36