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1.
The luminescence properties of Sr2–1.5x−1.5yP2O7:xDy3+,yCe3+ phosphor for near‐UV‐based white LEDs synthesized by a chemical co‐precipitation method
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A series of Sr2P2O7:Dy3+, Sr2P2O7:Ce3+ and Sr2P2O7:Dy3+,Ce3+ phosphors was synthesized via the one‐step calcination process for the precursors prepared by co‐precipitation methods. The phases, morphology, quantum efficiency and photoluminescence properties of the obtained phosphors were characterized systematically. These results show that the near‐spherical particles prepared through calcining the precursors by means of ammonium dibasic phosphate co‐precipitation (method 3) have the smallest particle size and strongest emission intensity among the three methods in the paper. With Dy3+ concentration increasing in Sr2P2O7:Dy3+ phosphors, the luminescence intensity first increases, reaches maximum, and then decreases. A similar trend was followed by Sr2P2O7:Ce3+ with Ce3+concentration increasing. A successful attempt was made to initiate the energy transfer mechanism from Ce3+ to Dy3+ in the host lattice and an overlap between the emission band of Ce3+ and the excitation band of Dy3+ indicated that the Ce3+ → Dy3+ energy transfer may indeed exist. It is clear that the photoluminescence intensity of Dy3+ as well as the quantum efficiency of the phosphor can be enhanced markedly by co‐doping Ce3+. Sr2P2O7:Dy3+,Ce3+ has its (CIE) chromaticity coordinates in the bluish‐white‐light region, near the standard illuminant D65. The CIE 1913 chromaticity coordinates of Sr2P2O7:Dy3+ phosphors fall in the white‐light region, and are adjacent to the ideal white‐light coordinates. In addition, the colour temperature and colour tone of Sr2P2O7:Dy3+ could be adjusted by changing the relative concentration of Dy3+. In short, Sr2P2O7:Dy3+ can be a promising single‐phased white‐light emitting phosphor for near‐UV (NUV) w‐LEDs. 相似文献
2.
Luminescent properties of single‐phase Ba2‐x‐1.5y‐1.5zP2O7:xEu2+,yCe3+, zTb3+ phosphors for white light‐emitting diode
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A series of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors was synthesized via a co‐precipitation method, then their crystal structure, quantum efficiency and luminescent properties were analyzed by XRD and FL, respectively. The results showed that these phosphors not only presented the excitation characteristics of Ba2P2O7:xEu2+,zTb3+, but also exhibited that of the Ba2P2O7:yCe3+,zTb3+ phosphor. Meanwhile, the tri‐doped phosphor showed a stronger absorption around 320 nm in contrast with the Eu2+/Ce3+:Tb3+ co‐doped phosphor. Not only can energy transfer from Ce3+→Eu2+ be observed; the energy transfer mechanism from Eu2+ to Tb3+ is discussed in the tri‐doped system. Ce3+ affects the luminescence properties of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors just as the sensitizer whereas Eu2+ is considered both as the sensitizer and the activator. The chromaticity coordinates of tri‐doped phosphors excited at 320 nm stayed steadily in the bluish‐white light region,and the emitted color and color temperature (CCT) of these phosphors could be tuned by adjusting the relative contents of Eu2+, Ce3+ and Tb3+. Hence, the single phase Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors may be considered as potential candidates for white light‐emitting diodes. 相似文献
3.
Effect of Mg doping in Sr2SiO4:Eu2+ nanophosphors for blue and white emission at near‐UV excitation
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Nanophosphors of (Sr0.98‐xMgxEu0.02)2SiO4 (x = 0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ ?doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation. However the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460 nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore, the (Mg0.78Sr0.20Eu0.02)2SiO4 nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green–yellow emission at 395 nm excitations. The Commission International de L'Eclairage (CIE) chromaticity coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in a 1:1 ratio) fall in the white region demonstrating the possible use of the mixture in white light generation using near‐UV excitation source. 相似文献
4.
Enhancement of the luminescence properties of Sr3(PO4)2:Dy3+,Li+ white‐light‐emitting phosphors by charge compensator Li+ co‐doping
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Sr3(PO4)2:Dy3+,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 Sr3(PO4)2, even when Dy3+ and Li+ were introduced. Under ultraviolet excitation at 350 nm, the Sr3(PO4)2:Dy3+ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. A white light was fabricated using these two emissions from the Sr3(PO4)2:Dy3+ phosphors. The luminescence properties of Sr3(PO4)2:Dy3+,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. 相似文献
5.
Hong Yu Wenwen Zi Shi Lan Shucai Gan Haifeng Zou Xuechun Xu Guangyan Hong 《Luminescence》2013,28(5):679-684
Sr3MgSi2O8:Ce3+, Dy3+ phosphors were prepared by a solid‐state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce3+ ions (403 nm) but also as a band due to Dy3+ ions (480, 575 nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce3+/Dy3+ co‐doped Sr3MgSi2O8 phosphors, and the co‐doping of Ce3+ could enhance the emission intensity of Dy3+ to a certain extent by transferring its energy to Dy3+. The Ce3+/Dy3+ energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94MgSi2O8:0.01Ce3+, 0.05Dy3+ phosphors, the fluorescence lifetime of Dy3+ (from 3.35 to 27.59 ns) is increased whereas that of Ce3+ is greatly decreased (from 43.59 to 13.55 ns), and this provides indirect evidence of the Ce3+ to Dy3+ energy transfer. The varied emitted color of Sr3MgSi2O8:Ce3+, Dy3+ phosphors from blue to white were achieved by altering the concentration ratio of Ce3+ and Dy3+. These results indicate Sr3MgSi2O8:Ce3+, Dy3+ may be as a candidate phosphor for white light‐emitting diodes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
Structural characterization of Er3+,Yb3+‐doped Gd2O3 phosphor,synthesized using the solid‐state reaction method,and its luminescence behavior
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We report the synthesis and structural characterization of Er3+,Yb3+‐doped Gd2O3 phosphor. The sample was prepared using the conventional solid‐state reaction method, which is the most suitable method for large‐scale production. The prepared phosphor sample was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermoluminescence (TL), photoluminescence (PL) and CIE techniques. For PL studies, the excitation and emission spectra of Gd2O3 phosphor doped with Er3+ and Yb3+ were recorded. The excitation spectrum was recorded at a wavelength of 551 nm and showed an intense peak at 276 nm. The emission spectrum was recorded at 276 nm excitation and showed peaks in all blue, green and red regions, which indicate that the prepared phosphor may act as a single host for white light‐emitting diode (WLED) applications, as verified by International de I'Eclairage (CIE) techniques. From the XRD data, the calculated average crystallite size of Er3+ and Yb3+‐doped Gd2O3 phosphor is ~ 38 nm. A TL study was carried out for the phosphor using UV irradiation. The TL glow curve was recorded for UV, beta and gamma irradiations, and the kinetic parameters were also calculated. In addition, the trap parameters of the prepared phosphor were also studied using computerized glow curve deconvolution (CGCD). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Solid‐state synthesis and luminescent properties of yellow‐emitting phosphor NaY(MoO4)2:Dy3+ for white light‐emitting diodes
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A yellow‐emitting phosphor NaY(MoO4)2:Dy3+ was synthesized using a solid‐state reaction at 550 °C for 4 h, and its luminescent properties were investigated. Its phase formation was studied using X‐ray powder diffraction analysis, and there were no crystalline phases other than NaY(MoO4)2. NaY(MoO4)2:Dy3+ produced yellow emission under 386 or 453 nm excitation, and the prominent luminescence was yellow (575 nm) due to the 4 F9/2→6H13/2 transition of Dy3+. For the 575 nm emission, the excitation spectrum had one broad band and some narrow peaks; the peaks were located at 290, 351, 365, 386, 426, 453 and 474 nm. Emission intensities were influenced by the Dy3+ doping content and a concentration quenching effect was observed; the phenomenon was also proved by the decay curves. Moreover, the Commission International de I'Eclairage chromaticity coordinates of NaY(MoO4)2:Dy3+ showed similar values at different Dy3+ concentrations, and were located in the yellow region. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
Luminescence and energy‐transfer properties of color‐tunable Ca2Mg0.25Al1.5Si1.25O7:Ce3+/Eu2+/Tb3+ phosphors for ultraviolet light‐emitting diodes
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Bo. Yuan Yanhua Song Ye. Sheng Keyan Zheng Qisheng Huo Xuechun Xu Haifeng Zou 《Luminescence》2016,31(2):453-461
A series of Ca2Mg0.25Al1.5Si1.25O7:Ce3+/Eu2+/Tb3+ phosphors was been prepared via a conventional high temperature solid‐state reaction and their luminescence properties were studied. The emission spectra of Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Eu2+ and Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Tb3+ phosphors show not only a band due to Ce3+ ions (409 nm) but also as a band due to Eu2+ (520 nm) and Tb3+ (542 nm) ions. More importantly, the effective energy transfer from Ce3+ to Eu2+ and Tb3+ ions was confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and energy transfer mechanism were investigated and were demonstrated to be of resonant type via dipole–dipole (Ce3+ to Eu2+) and dipole–quadrupole (Ce3+ to Tb3+) reactions, respectively. Under excitation at 350 nm, the emitting color could be changed from blue to green by adjusting the relative doping concentration of Ce3+ and Eu2+ ions as well as Ce3+ and Tb3+ ions. The above results indicate that Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Eu2+/Tb3+ are promising single‐phase blue‐to‐green phosphors for application in phosphor conversion white‐light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
Sushant Rajendra Bargat Yatish Ratn Parauha Nayana Sudhakar Shirbhate Girish Mishra Sanjay Janaraoji Dhoble 《Luminescence》2022,37(3):463-471
In the recent few years, Eu2+- and Mn4+-activated phosphors are widely used as potential colour converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we synthesized novel red colour-emitting Ca(2−x)Mg2(SO4)3:xmol% Eu2+ (x = 0–1.0 mol%) phosphors via a solid-state reaction method in a reducing atmosphere. The photoluminescence (PL) excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm, and 554 nm. Under these excitations, emission spectra exhibited a broad band in the red colour region at ~634 nm. The PL emission intensity was measured for different concentrations of Eu2+. The maximum Eu2+ doping concentration in the Ca2Mg2(SO4)3 host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole–dipole interaction was responsible for the concentration quenching. The luminous red colour emission of the sample was confirmed using Commission international de l'eclairage colour coordinates. The results of PL excitation and emission spectra of the prepared phosphors were well matched with excitation and emission wavelengths of phytochrome PR. Therefore, from the entire investigation and obtained results it was concluded that the synthesized Ca0.995Mg2(SO4)3:0.5mol%Eu2+ phosphor has huge potential for plant cultivation application. 相似文献
10.
A solid‐state reaction route‐based LiTi2 ? xEux(PO4)3 was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi2 ? xEux(PO4)3 phosphor was excited at λexci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the 5D0 → 7F1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5D0 → 7F2), which is an electric dipole (ΔJ = ±2) transition of the Eu3+ ion. Beside this, excitation and emission spectra of host LiTi2(PO4)3 powder were also reported. The effect of Eu3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi2 ? xEux(PO4)3 phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu3+ ions in the host lattice. The LiTi2 ? xEux(PO4)3 phosphor displayed a reddish‐orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
11.
Synthesis and luminescence of Eu3+‐doped in triple phosphate Ca8MgBi(PO4)7 with whitlockite structure
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Triple whitlockite‐type structure‐based red phosphors Ca8MgBi1?x(PO4)7:xEu3+ (x = 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid‐state reaction route and characterized by their X‐ray crystal structures. The X‐ray diffraction (XRD) patterns, Fourier transform infrared spectra, morphologies, photoluminescence spectra, UV/Vis reflectance spectra, decay times and the International Commission on Illumination (CIE) chromaticity coordinates of Ca8MgBi1?x(PO4)7:xEu3+ were analyzed. Eu‐doped Ca8MgBi(PO4)7 phosphors exhibited strong red luminescence with peaks at 616 nm due to the 5D0 → 7 F2 electric dipole transition of Eu3+ ions after excitation at 396 nm. The UV/Vis spectra indicated that the band gap of Ca8MgBi0.30(PO4)7:0.70Eu3+ is larger than that of Ca8MgBi(PO4)7. The phosphor developed in this study has great potential as a red‐light‐emitting phosphor for UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
Eu3+‐activated MAl(SO4)2Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X‐ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu3+‐doped SrAl(SO4)2Br and MgAl(SO4)2Br phosphors exhibited characteristic red emission coming from the 5D0 → 7F2 (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu3+. The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO4)2Br:Eu3+, (M = Mg, Sr) phosphors have potential application in near‐UV light‐emitting diodes as efficient red‐emitting phosphor. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
Luminescence enhancement of (Sr1–xMx)2SiO4:Eu2+ phosphors with M (Ca2+/Zn2+) partial substitution for white light‐emitting diodes
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Eu2+‐doped Sr2SiO4 phosphor with Ca2+/Zn2+ substitution, (Sr1–xMx)2SiO4:Eu2+ (M = Ca, Zn), was prepared using a high‐temperature solid‐state reaction method. The structure and luminescence properties of Ca2+/Zn2+ partially substituted Sr2SiO4:Eu2+ phosphors were investigated in detail. With Ca2+ or Zn2+ added to the silicate host, the crystal phase could be transformed between the α‐form and the β‐form of the Sr2SiO4 structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f65d1 → 4f7 transition of Eu2+ ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu2+ ions occupying the ten‐fold oxygen‐coordinated Sr.(I) site and the nine‐fold oxygen‐coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr2SiO4:Eu2+ phosphors, improved remarkably on Ca2+/Zn2+ addition, and promote its application in white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
14.
A new system for the determination of nucleic acid by rare earth metallic porphyrin of [tetra‐(3‐methoxy‐4‐hydroxyphenyl)]–Tb3+ [T(3‐MO‐4HP)–Tb3+] porphyrin as fluorescence spectral probe has been developed in this paper. Nucleic acid can enhance the fluorescence intensity of the T(3‐MO‐4HP)–Tb3+ porphyrin in the presence of bis(2‐ethylhexyl)sulfosuccinate sodium salt(AOT) micelle. In pH 8.00 Tris–HCl buffer solution, under optimum conditions, the enhanced fluorescence intensity is in proportion to the concentration of nucleic acids in the range of 0.05–3.00 µg mL?1 for calf thymus DNA (ct DNA) and 0.03–4.80 µg mL?1 for fish sperm DNA(fs DNA). Their detection limits are 0.03 and 0.01 µg mL?1, respectively. In addition, the binding interaction mechanism between T(3‐MO‐4HP)–Tb3+ porphyrin and ct DNA is also investigated by resonance scattering and fluorescence spectra. The maximum binding number is calculated by molar ratio method. The new system can be used for the determination of nucleic acid in pig liver, yielding satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献