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1.
Formation mechanism and optimized luminescence of Mn4+‐doped unequal dual‐alkaline hexafluorosilicate Li0.5Na1.5SiF6
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Mengmeng Zhu Yuexiao Pan Xi'an Chen Hongzhou Lian Jun Lin 《Journal of the American Ceramic Society》2018,101(11):4983-4993
A novel red phosphor Li0.5Na1.5SiF6:Mn4+ (LNSF:Mn) based on the unequal dual‐alkaline hexafluorosilicate with superior optical performances has been synthesized via ion‐exchange between [MnF6]2? and [SiF6]2? at room temperature. The composition and the crystal structure of the as‐obtained phosphor LNSF:Mn were determined by energy‐dispersive x‐ray spectroscopy (EDS) and x‐ray diffraction (XRD), respectively. The formation mechanism of the red phosphor LNSF:Mn has been discussed in detail. The phosphor LNSF:Mn exhibits good chromaticity properties and a quantum yield (QY) of 96.1%, which are better than the identified fluorosilicate phosphors Na2SiF6:Mn4+ (NSF:Mn) and K2SiF6:Mn4+ (KSF:Mn). A broad and intense absorption in the blue and a bright emission in red‐shifted wavelengths make the phosphor LNSF:Mn a desired candidate for applications in warm white light‐emitting diodes. 相似文献
2.
Wavelength converters in white light-emitting diodes are usually made by sintering of phosphor-glass powder compacts. An issue is that the sintering process usually results in the reduction of phosphor amount. In the present study, composites containing CaAlSiN3:Eu2+ red phosphor and Bi2O3-B2O3-ZnO-Sb2O5 glass were fabricated by sintering method. Influences of CaAlSiN3:Eu2+ phosphor content (10 vol%–30 vol%) and sintering temperature (410–430°C) on the residual amount of the phosphor phase and the resulting luminescence intensity of the composites were investigated. The change of CaAlSiN3:Eu2+ content due to sintering was analyzed by X-ray diffraction. The interdiffusion between the CaAlSiN3:Eu2+ and glass matrix was examine by scanning electron microscope equipped with energy dispersive X-ray spectrometry. This paper focuses on the change of luminescence intensity after sintering. It was found that although the content of phosphor CaAlSiN3:Eu2+ reduces after sintering; the luminescent intensity of the composites anomalously increases. The optimum luminescence intensity is 14% higher than that of the as-mixed, unfired powder. It is proposed that the incorporation of Bi3+ ions from the glass matrix into the phosphor CaAlSiN3:Eu2+ during sintering improves the luminescence ability of the phosphor particles. 相似文献
3.
《Ceramics International》2016,42(15):16852-16860
Green light emitting Zn2SiO4:Mn2+ phosphors have been synthetised by the solid-state reaction in ambient atmosphere at 1300 °C for 2 h, with ZnO, SiO2 and MnO2 as the reagents. The ZnO/SiO2 molar ratio varied from 2 to 0.5. The doping level was in a lower concentration range (0.01≤x≤0.05). The effect of both the Mn2+ concentration and ZnO/SiO2 molar ratio on luminescence intensity and decay was investigated in detail. The microstructure and phase composition of prepared phosphors were characterised by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). XRD results indicate that the pure α-Zn2SiO4 phase with rhombohedral structure was obtained after heat treatment. The prepared phosphors exhibit a strong green emission centred at 525 nm from the 4T1→6A1 forbidden transition. The highest emission intensity was observed for phosphors with ZnO/SiO2 molar ratio equal to 1.0, and the Mn2+ concentration x=0.03 (ZSMn3). The emission intensity of the ZSMn3 phosphor is comparable with the commercial Zn2SiO4:Mn2+ phosphor. The decay curves can be characterised by double exponential function. After fitting a fast component τ1∼2 ms and a slow component τ2∼10 ms were obtained. The decay times decrease significantly with increasing Mn2+ concentration. The decay time and luminescence mechanism depend on the excitation light wavelength. Temperature dependent luminescence of the ZSMn3 phosphor in the temperature range of 25–200 °C was studied. 相似文献
4.
Color tunable yellow-emitting phosphors of Sr5−5xEu5x(PO4)2SiO4 (x = 0.05-0.15) were prepared by conventional solid-state reaction method. The X-ray powder diffraction patterns, the photoluminescence excitation and emission spectra were measured. The main excitation bands of the phosphors locate at a broad band extending from 300 to 500 nm, which can match the emission of ultraviolet- and blue-emitting diode chips. The tunable luminescence color was realized by the changing Eu2+ doping in Sr5(PO4)2SiO4. The structure and luminescence properties were investigated. Sr5−5x(PO4)2SiO4:Eu5x displays two typical luminescence centers, which originate from two different Sr2+ (Eu2+) sites in the host. The site-occupation, the luminescence intensity and energy transfer between the Eu2+ ions occupying two different crystallographic Sr2+ sites were discussed on the base of the luminescence spectra and crystal structure. This is helpful to improve this phosphor for a potential application as a white light emitting diode phosphor. 相似文献
5.
An effective way of improving photoluminescence (PL) of YAG:Ce by addition of small amount of SiC and sintering in air was described. The breakdown of SiC during sintering process in air was employed to provide the presence of SiO2 and CO both of which are known to be beneficial in enhancing the PL of YAG:Ce phosphor. SiC in the form of a fine powder was added to YAG:Ce powder and sintered to densities of >99% of theoretical density. The highest luminescence was measured in sample containing 0.08?wt% SiC. The effect of the formed SiO2 and CO was discussed and their contribution to the emission intensity was assessed. The enhancement of PL intensity is attributed to the formation of vacancies, both on Y sub-lattice and on oxygen sub-lattice and their ability to release the electrons for subsequent reduction of Ce4+ to Ce3+ which plays a role of luminescence activator. 相似文献
6.
U. Rambabu N.R. Munirathnam S. Chatterjee B. Sudhakar Reddy Sang-Do Han 《Ceramics International》2013,39(5):4801-4811
Enhanced red luminescence in LnVO4: Bi3+, Eu3+ @ SiO2 phosphors has been improved mainly in three stages by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) co-doping Bi3+ as a sensitizer and finally (iii) SiO2 shell coating. XRD data revealed that the produced phosphors possess crystalline, pure phase with tetragonal structure. Silica coating on phosphor particles have been characterized by SEM/EDAX, TEM, PL and with the presence Si–O–Si, Si–O vibrational modes from the FT-IR spectra. Absorption band edges due to VO43?, shifted to higher wavelength with Bi-concentration, owing to the presence of Bi–O bond in addition to V–O. The emission intensities of 5D0→7F2 transition are stronger than 5D0→7F1; indicating the lower inversion symmetry near Eu3+, ions. Red emission intensity due to the efficient energy transfer from VO43? to Eu3+ via Bi3+ ions in Y0.949VO4: Bi3+0.001, Eu3+0.05 phosphor was improved significantly, i.e. 1.6 times compared to Y0.95VO4: Eu3+0.05. This was further enhanced 2.25 times by SiO2 shell coating. Thus, Y0.949VO4: Bi3+0.001, Eu3+0.05 @ SiO2 are suggested to be a promising red phosphor for application in display devices or lighting. 相似文献
7.
Zhiyong Fang Xiaohui Lai Jian Zhang Rui Zhang 《International Journal of Applied Ceramic Technology》2021,18(4):1106-1113
K2TiF6:Mn4+ is an attractive narrow-band red-emitting phosphor for warm white light-emitting diodes (LEDs). Nevertheless, the hexafluoride phosphor is liable to deliquesce in moist environments, which leads to a sharp deterioration performance of luminescence. Surface modification of K2TiF6:Mn4+ phosphor with SrF2 coating has been introduced, with the aid of KHF2 transition layer to moderate the lattice mismatch. The reaction mechanism is discussed in detail, as so as the influence of SrF2 coating on the luminescence intensity. The SrF2 coating is able to prevent the hydrolysis of internal [MnF6]2− group; thereby, the luminescence intensity retains over 90% of initial value after being immersed in distilled water for 2 h. The LED devices fabricated with commercial Y3Al5O12:Ce3+ and as-modified K2TiF6:Mn4+ phosphors exhibit bright white light with tunable chromaticity coordinate, correlated color temperature, and color rendering index. It enlightens a convenient method to enhance the moisture resistance of Mn4+ doped fluoride phosphors for commercial application in the field of white LEDs. 相似文献
8.
《Ceramics International》2023,49(8):12088-12096
Mn4+ activated fluoride red phosphors, as candidate red materials in white light-emitting diodes (WLEDs), have received widespread attention. However, the poor water stability limits their application. Herein, a novel dodec-fluoride red phosphor Na3Li3In2F12:Mn4+ with good waterproof stability was successfully synthesized by solvothermal method. The crystal structure, optical property, micro-morphology, element composition, waterproof property and thermal behavior of Na3Li3In2F12:Mn4+ phosphor were analyzed. Under the 468 nm blue light excitation, the Na3Li3In2F12:Mn4+ phosphor has narrow emission bands in the area of 590–680 nm. Compared with commercial red phosphor K2SiF6:Mn4+, the Na3Li3In2F12:Mn4+ phosphor possesses better waterproof stability. When soaked in water for 360 min, the PL intensity of the Na3Li3In2F12:Mn4+ phosphor remains at initial 80%. Finally, warm WLEDs with CRI of 87 and CCT of 3386 K have been fabricated using blue InGaN chip, YAG:Ce3+ yellow phosphor and Na3Li3In2F12:Mn4+ red phosphor. 相似文献
9.
Myoung Gyu Ha Jae-Sun Jeong Kyoung-Rim Han Yangsoo Kim Ho-Soon Yang Euh Duck Jeong K.S. Hong 《Ceramics International》2012,38(7):5521-5526
Optical properties of samarium-doped strontium orthosilicate for near ultra-violet excitation are studied. Sr2SiO4:Sm3+ phosphor is synthesized by using the solid-state reaction method. The structure and physical properties of the phosphor are characterized by using X-ray diffractometer, scanning electron microscope, UV–visible spectrophotometer, high-resolution secondary ion mass spectrometer, and X-ray photoelectron spectrometer. Optical properties are studied by taking excitation and emission spectra. A strong red-orange luminescence corresponding to 4G5/2 → 6H7/2 transition of Sm3+ for near ultra-violet excitation is observed. It is found that Sr2SiO4:Sm3+ is a red-orange emitting phosphor and has higher efficiency for the operation with near ultra-violet excitation. 相似文献
10.
《Ceramics International》2023,49(20):33316-33323
Y2O3: x% Er3+ (x=5, 7, 10, 12, 15) and Y2O3: 10% Er3+,x% K+ (x=0, 1, 3, 5, 7, 10, 15) phosphors were successfully prepared by a low-temperature combustion method. The structure as well as the absorption/emission spectra of phosphors were investigated. The effect of doping concentration of K+ ions on the upconversion (UC) luminescence of Y2O3: 10% Er3+ phosphor was examined and the possible optical transitions were discussed. The results showed that K+ ion doping not only changed the microstructure and crystallinity of the phosphors, but also enhanced its UC luminescence intensity. The Y2O3: 10% Er3+, 7% K+ phosphor exhibit the strongest UC emission intensity. Compared with the Y2O3: 10% Er3+ phosphor, the UC luminescence intensity at 563 nm and 661 nm was enhanced by 67.8 and 27.3 times for the K-codoped samples, respectively. The phosphor with the optimal doping concentration was mixed with a polymer to form a composite film, which was employed for the fabrication of near-infrared (NIR) photo-responsive detection devices. The device exhibited strong photo-current response to NIR light at 980 nm, implying that our work could inspire new design strategy for the development of NIR photo-detection devices. 相似文献
11.
Photoluminescence Enhancement of SiO2‐Coated LaPO4:Eu3+ Inverse Opals by Surface Plasmon Resonance of Ag Nanoparticles
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Jun Li Zhengwen Yang Bo Shao Jianzhi Yang Yida Wang Jianbei Qiu Zhiguo Song 《Journal of the American Ceramic Society》2016,99(10):3330-3335
The surface plasmon resonance of Ag nanoparticles (NPs) and SiO2 coating had been extensively employed to improve the photoluminescence (PL) intensity of nanomaterials. In the article, the LaPO4:Eu3+ inverse opal photonic crystals were fabricated via combining a self‐assembly process with a sol–gel method. The SiO2 shells were formed on the skeleton surface of LaPO4:Eu3+ inverse opals and the Ag NPs were added into the voids of LaPO4:Eu3+ inverse opals with the SiO2 shells. The influence of the SiO2 shells and Ag NPs on the PL of the LaPO4:Eu3+ inverse opals were investigated. About sevenfold luminescence enhancement of LaPO4:Eu3+ inverse opals was obtained by the coordination action of surface plasmon absorption effects of Ag nanoparticle and silica‐coating effects. The luminescence enhancement mechanisms of LaPO4:Eu3+ inverse opals were discussed. 相似文献
12.
《Ceramics International》2016,42(6):6846-6849
Eu2+-activated LiSr3SiO4Cl3 phosphors were successfully designed, and prepared at low calcination temperature (650 °C). The crystal structure, morphology, and photoluminescence properties have been investigated in detail. The LiSr3SiO4Cl3 crystallizes in orthorhombic LiEu3SiO4Cl3-type structure. Under 316 nm excitation, the phosphor exhibits an asymmetric emission band peaking at 495 nm, which is probably attributed to the 4f–5d transitions of Eu2+ in various crystallographic sites. Their luminescence properties are investigated as a function of activator concentration (Eu2+). The quenching concentration of Eu2+ in LiEu3SiO4Cl3 is about 0.01 due to dipole–dipole interaction. The investigation indicates that Eu2+-activated LiEu3SiO4Cl3 phosphor can be used as a green emitting phosphor for white LEDs. 相似文献
13.
Synthesis,Crystal Structure,and Luminescence Properties of Y4Si2O7N2: Eu2+ Oxynitride Phosphors
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Guozhang Chen Liang‐Jun Yin Jun‐Tao Dong Yan‐Yu Feng Yang Gao Weidong He Yu Jia Xin Xu Hubertus T. Hintzen 《Journal of the American Ceramic Society》2016,99(1):183-190
Y4Si2O7N2: Eu2+ phosphor has been prepared by a pretreatment method. Reduction in Eu3+ ions into Eu2+ by the use of hydrogen iodide (HI) is verified by X‐ray absorption near‐edge structure (XANES) and electrode potential analysis. Y4Si2O7N2: Eu2+ phosphor has a broad emission band in the range of 400–500 nm. Furthermore, the effect of Zr doping on the structure and luminescence properties of Y4Si2O7N2: Eu2+ phosphor is researched. It found that the Zr doping leads to an emission blueshift, and improves the luminescence intensity and thermal quenching behavior of Y4Si2O7N2: Eu2+ phosphors. Prospectively, the pretreatment approach could be extended to develop other Eu2+‐doped compounds. 相似文献
14.
Eu2+-activated Ba2CaMg2Si6O17 phosphors were synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurement. The photoluminescence excitation and emission spectra were investigated. The phosphor presents blue-emitting luminescence. The crystallographic sites of Eu2+ ions in Ba2CaMg2Si6O17 host were discussed on the base of luminescence properties and the crystal structure. The lightly Eu2+-doped sample shows one luminescence center for the Eu2+ ions on Ba2+ sites, while there are two luminescence centers for the Eu2+ ions on both the Ba and Ca sites in heavily Eu2+-doped sample. The dependence of luminescence intensity on temperatures and the activation energy (ΔE) for the thermal quenching were reported. The phosphor shows an excellent thermal stability on temperature quenching because of the special layered structure of Ba2+ ions in the interlayer between SiO4 layers. 相似文献
15.
《Ceramics International》2017,43(12):9084-9091
This paper reports the preparation of Eu3+ doped Gadolinium oxyorthosilicate (Gd2SiO5:Eu3+) phosphor with different concentration of Eu3+(0.1–2.5 mol%) using the modified solid state reaction method. The synthesis procedure of the Gd2SiO5:Eu3+phosphor using inorganic materials such as Gd2O3, silicon dioxide (SiO2), europium oxide (Eu2O3) and boric acid (H3BO3) as flux is discussed in detail. The prepared phosphor samples were characterized by using X-Ray Diffraction (XRD), Field Emission Gun Scanning Electron Microscopy (FEGSEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence (PL) and Thermoluminescence (TL). The Commission Internationale de l′Eclairage(CIE) coordinates were also calculated. The PL emission was observed in the 350–630 nm range for the Gd2SiO5:Eu3+ phosphor. PL excitation peaks were observed at 266, 275, 312 and 395 nm while the emission peaks were observed at 380, 416, 437, 545, 579, 589, 607, 615 and 628 nm. The emission peak at 615 nm was the most intense peak for all the different Eu3+ concentration samples. From the XRD data, using the Scherrer's formula, the average crystallite size of the Gd2SiO5:Eu3+ phosphor was calculated to be 33 nm. TL was carried out for the phosphor after both UV and gamma irradiation. The TL response of the Gd2SiO5:Eu3+ phosphor for the two different radiations was compared and studied in detail. It was found that the present phosphor can acts as a single host for red emission (1.5 mol%) for display devices and light emitting diode (LED) and white light emission for Eu3+(0.1 mol%) and it might be used as a TL dosimetric material for gamma dose detection. 相似文献
16.
《Ceramics International》2023,49(13):21864-21871
Cr3+ doped phosphor shows great potential for near-infrared (NIR) light-emitting diodes (LED), but it suffers from low quantum efficiency and poor thermal stability. Herein, a novel Cr3+ doped broadband NIR garnet Ca3Sc2Ge3O12 phosphor was developed. The multisite structure of the emission band is investigated by site-selective spectroscopy and is attributed to the octahedral Cr3+ perturbed by defects. Moreover, we propose different strategies to enhance the luminescence of the phosphor, including enhancement of crystallinity and elimination of defects. Compared with the initial sample, the emission intensity of the optimized phosphor is improved for 8.6 times. The optimal Ca3Sc2Ge3O12: 0.06Cr3+ phosphor exhibits excellent thermal stability. At 423 K, the integral emission intensity of the optimal sample remains 94.7% of that at room temperature. Finally, high-performance NIR LED was fabricated using a blue LED and the title phosphor. The packaged LED lamp has high radiance (109.3 mW@300 mA) and photoelectric efficiency (15.96%@40 mA). Our study not only provides a boulevard for enhancing the luminescence of Cr doped NIR phosphor, but also gives a new perspective for understanding the multisite luminescence of Cr3+ in garnet host. 相似文献
17.
α′- and β-Sr2SiO4:Eu2+ phosphor powders were prepared by spray pyrolysis from the spray solutions with and without NH4Cl flux. The phosphor powders prepared from the spray solutions with the addition amount of NH4Cl flux between 2 and 5 wt% of phosphor had regular polyhedron structures and main crystal structure of β-Sr2SiO4. On the other hand, the phosphor powders prepared from the spray solution with high addition amount of NH4Cl flux as 6 wt% of phosphor had irregular morphology and crystal structure of α′-Sr2SiO4. The mean size of the β-Sr2SiO4 phosphor powders with regular polyhedron structure was 5.2 μm. The β-Sr2SiO4:Eu2+ phosphor powders had higher photoluminescence intensities than the α′-Sr2SiO4:Eu2+ phosphor powders. The β-Sr2SiO4:Eu2+ phosphor powders prepared from the spray solution with 5 wt% NH4Cl flux of phosphor had the maximum photoluminescence intensity. The wavelengths of the emission spectra showing the maximum peak intensities changed from 543.2 to 561.8 nm when the addition amount of NH4Cl flux was increased from 2 to 6 wt% of phosphor. 相似文献
18.
Optimized photoluminescence of red phosphor Na2SnF6:Mn4+ as red phosphor in the application in “warm” white LEDs
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Luqing Xi Yuexiao Pan Xian Chen Shaoming Huang Mingmei Wu 《Journal of the American Ceramic Society》2017,100(5):2005-2015
The Mn4+ activated fluostannate Na2SnF6 red phosphor was synthesized from starting materials metallic tin shots, NaF, and K2MnF6 in HF solution at room temperature by a two‐step method. The formation mechanism responsible for preparing Na2SnF6:Mn4+ (NSF:Mn) has been investigated. The influences of synthetic parameters: such as concentrations of HF and K2MnF6 in reaction system, reaction time, and temperature on crystallinity, microstructure, and luminescence intensity of NSF:Mn have been investigated based on detailed experimental results. The actual doping concentration of Mn4+ in the NSF:Mn host lattice is less than 0.12 mol%. The most of K2MnF6 is decomposed in HF solution especially in hydrothermal system at elevated temperatures. The color of the as‐prepared NSF:Mn samples changes from orange to white when the temperature is higher than 120°C, which indicates the lower concentration of luminescence centers in the crystals. A series of “warm” white light‐emitting diodes with color rendering index (CRI) higher than 88 and correlated color temperatures between 3146 and 5172 K were obtained by encapsulating the as‐prepared red phosphors NSF:Mn with yellow one Y3Al5O12:Ce3+ (YAG:Ce) on 450 nm blue InGaN chips. The advantage of the synthetic strategy to obtain NSF:Mn can be extended to developing Mn4+‐doped red phosphors from low‐costing metals at room temperature for large‐scale industrial applications. 相似文献
19.
《Ceramics International》2016,42(7):8240-8246
Aeschynite-type EuTiNbO6 fine phosphor with sufficient luminescence intensity was directly formed as homogeneous cuboid particles with high crystallinity in the range of 1–2 μm from precursor solution mixtures of EuCl3, TiOSO4, and NbCl5 under weakly basic conditions via hydrothermal treatment at 240 °C for 5 h. The as-prepared aeschynite phase stably existed after heating at 1000–1400 °C for 1 h in air. Under excitation at wavelengths of 395 nm, among all samples before and after heating in air, the as-prepared EuTiNbO6 fine crystals before heating emitted luminescence with the highest intensity in the red spectral region with strong red and weak orange light corresponding to 5D0→7F2 and 5D0→7F1 transitions of Eu3+, respectively. The amorphous coprecipitation powder crystallized into euxenite-type phase at 700–1000 °C and transformed into aeschynite-type phase at 1000–1200 °C. High-temperature heating at 1400 °C was essential for the coprecipitation powder to obtain almost a single phase of aeschynite-type EuTiNbO6 and sufficient emission intensity. 相似文献
20.
《Ceramics International》2023,49(10):15341-15348
A series of Dy3+-activated Ba2La8(SiO4)6O2 phosphors were synthesized using the solid-state method with the objective of developing single host white light emitting phosphors for use in solid state lighting applications. The Dy3+ concentration varied between 0.01 and 0.05 mol%. The as-prepared phosphors crystal structure, optical, and photoluminescent properties (PL), along with energy transfer mechanism and luminescence decay, were investigated. The production of a single-phase Ba2La8(SiO4)6O2 with hexagonal symmetry was verified by the findings of the X-ray diffraction analysis. When the Ba2La8(SiO4)6O2: Dy3+ phosphors are exposed to ultraviolet light, they emit the characteristic yellow PL emissions caused by the 4F9/2 → 6H13/2 transition. The Judd-Ofelt (J-O) parameters (Ω2, Ω4, Ω6) were computed using the excitation spectra. The characteristics of the Dy3+ transition indicate that the asymmetric environment around the ligand was suggested by the trend, which was followed by J-O parameters. Due to the dominance of the electric-dipole transition in the luminescence spectrum, the Ba2La8(SiO4)6O2:0.03Dy3+ phosphor displayed yellowish white emission with CIE coordinates of (0.358, 0.398) and a CCT of 4724 K. The synthesized phosphor may be a useful material in the fabrication of white-emitting phosphor for LEDs application. 相似文献