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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hu T., Molokeev M. S., Xia Z., Zhang Q.
Заглавие : Aliovalent substitution toward reinforced structural rigidity in Ce3+-doped garnet phosphors featuring improved performance
Место публикации : J. Mater. Chem. C. - 2019. - Vol. 7, Is. 46. - P.14594-14600. - ISSN 20507534 (ISSN), DOI 10.1039/c9tc05354a
Примечания : Cited References: 38. - This work was supported by the National Natural Science Foundation of China (No. 51722202 and 51972118), the Guangdong Provincial Science & Technology Project (2018A050506004) and the Fundamental Research Funds for the Central Universities (D2190980).
Аннотация: Highly efficient phosphors with thermal stability and color-tunable emission are required for the fabrication of phosphor-converted white light-emitting diodes (pc-WLEDs). Currently developed engineering strategies are generally successful in photoluminescence tuning but, unfortunately, suffer severe deterioration in emission intensity/efficiency and/or thermal stability. Herein, an efficient aliovalent substitution strategy toward reinforced structural rigidity is proposed and demonstrated experimentally. By incorporating Be2+ ion into the garnet-type Lu2SrAl4SiO12:Ce3+ phosphor, the phosphor shows enhanced internal/external quantum efficiency, from 79.2%/26.7% to 84.5%/32.9%, photoluminescence tuning from green (peaking at ∼512 nm) to yellow (peaking at ∼552 nm), and zero thermal quenching, even up to 200 °C. The Be2+ substitution at the Al2/Si2 site enables stable and rigid local surroundings around the Ce3+ activator, which is responsible for the unprecedented performance. In addition, high-quality warm WLED devices with a luminous efficiency of 158.1 lm W-1, correlated color temperature of 3858 K and high color rendering index of 81.7, are obtained by combining Lu2SrAl4SiO12:Ce3+,Be2+ as the yellow emitter, CaAlSiN3:Eu2+ as the red emitter and a blue-emitting InGaN chip. These findings highlight a new strategy for performance optimization of LED phosphors by selecting rigid covalent compounds with further reinforced structural rigidity via aliovalent substitution.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wu, Yanzheng, Li, Weiqiang, Zheng, Yifan, Xu, Yiqin, Wen, Dawei, Molokeev M. S., Pan, Zaifa
Заглавие : Apatite oxynitride phosphor (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+: A single-phased host with solar-like and efficient emission
Место публикации : J. Am. Ceram. Soc. - 2023. - Vol. 106, Is. 5. - P.2985-2996. - ISSN 00027820 (ISSN), DOI 10.1111/jace.18981. - ISSN 15512916 (eISSN)
Примечания : Cited References: 35. - This work was supported by the National Natural Science Foundation of China (Project No. 10804099, 21804119), Key projects of Zhejiang Natural Science Foundation (Project No. LZ18B050002), GDAS’ Project of Science and Technology Development (Nos. 2021GDASYL-20210103069, 2021GDASYL-20210103071)
Аннотация: During pursuing high color rendering index for full-color-emitting phosphor, low quantum efficiency (QE) is usually accompanying. We intend to elevate the luminescence efficiency when realizing a solar-like spectra distribution, by constructing apatite structure oxynitride, inheriting high covalence and rigidity from oxynitride, and suitable multiple cation sites from oxyapatite compounds. Full-color-emitting apatite structure oxynitride phosphor (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ has been prepared, and the crystal sites’ occupancies of activators in this host were favorable for white emission. (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ phosphor shows whole visible light with emission wavelength ranging from 370 to 750 nm, matching the spectra of sunlight quite well. The fabricated white light-emitting diode lamp demonstrated the distinctive overall performance of QE and chromaticity properties (Ra and R9). Furthermore, correlated color temperature is tunable from cool nature to warm white. The obtained lamp possesses the feature of less blue light hazard and high saturation of red degree, compared with the commercial YAG-based lamp.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang Z. Y., Xia, Zhiguo, Molokeev M. S., Atuchin V. V., Liu Q. L.
Заглавие : Blue-shift of Eu2+ emission in (Ba,Sr)3Lu(PO4)3:Eu2+ eulytite solid-solution phosphors resulting from release of neighbouring-cation-induced stress
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2014. - Vol. 43, Is. 44. - P.16800-16804. - ISSN 1477-9226, DOI 10.1039/c4dt02319f. - ISSN 1477-9234
Примечания : Cited References: 16. - The present work was supported by the National Natural Science Foundations of China (grant no. 51002146, no. 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635) and the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306). V.V.A. is partly supported by the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: TUNABLE COLOR TONE
EXCITED WHITE LEDS
CRYSTAL-STRUCTURE
TEMPERATURE
IONS
Аннотация: A series of iso-structural eulytite-type (Ba,Sr)(3)Lu(PO4)(3):Eu2+ solid-solution phosphors with different Sr/Ba ratios were synthesized by a solid-state reaction. Crystal structures of (Ba,Sr)(3)Lu(PO4)(3):Eu2+ were resolved by the Rietveld method, which shows an eulytite-type cubic Bi-4(SiO4)(3) structure with cations disordered in a single C-3 site while the oxygen atoms were distributed over two partially occupied sites. The emission peaks of Ba(3-x)SrxLu(PO4)(3):Eu2+ (0
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu Q., Dang P., Zhang G., Lian H., Li G., Molokeev M. S., Cheng Z., Lin J.
Заглавие : Broad luminescence tuning in Mn2+-doped Rb2Zn3(P2O7)2 via doping level control based on multiple synergies
Место публикации : CrystEngComm. - 2022. - Vol. 24, Is. 31. - P.5622-5629. - ISSN 14668033 (ISSN), DOI 10.1039/d2ce00719c
Примечания : Cited References: 31. - We acknowledge the financial support from the National Natural Science Foundation of China (NSFC No. 51932009, 51720105015, 51929201, 52072349, and 52172166), Projects for the Science and Technology Development Plan of Jilin Province (20210402046GH), and the Natural Science Foundation of Zhejiang Province (LR22E020004)
Аннотация: Here we constructed a series of novel non-centrosymmetric structure phosphors [Rb2Zn3(P2O7)2:Mn2+] by a high-temperature solid-state reaction. The multiband emission can be designed by Mn2+ preferentially occupying three types of crystallographic sites in Rb2Zn3(P2O7)2:Mn2+. The emission color could be continuously tuned from yellow-green to orange-red via multiple synergies among crystallographic site engineering, energy transfer, and Mn-Mn dimmers alone through the dopant concentration. These color-tunable phosphors have good thermal stability (I150 °C/I25 °C = 91%). The as-prepared pc-WLED has a low corresponding color temperature (CCT = 4820 K) and a high color rendering index (Ra = 90.4) with CIE color coordinates of (0.351, 0.358). These results show that emission-tunable Rb2Zn3(P2O7)2:xMn2+ phosphors are potential candidates for application in n-UV-based pc-WLED devices. This study offers a new insight for wide-range tuning of PL properties by using crystallographic site engineering through changing the doping level in Mn-activated phosphors.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ji H. P., Huang Z. H., Xia, Zhiguo, Molokeev M. S., Atuchin V. V., Huang S. F.
Заглавие : Cation substitution dependent bimodal photoluminescence in whitlockite structural Ca3-xSrx(PO4)2:Eu2+ (0 ≤ x ≤ 2) solid solution phosphors
Место публикации : Inorg. Chem.: American Chemical Society, 2014. - Vol. 53, Is. 20. - P.11119-11124. - ISSN 0020-1669, DOI 10.1021/ic501679f. - ISSN 1520-510X
Примечания : Cited References: 37. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51032007, 51002146, 51272242), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130022110006), the Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), and Beijing Youth Excellent Talent Program (YETP0635). V.V.A. acknowledges the Ministry of Education and Science of the Russian Federation for financial support.
Предметные рубрики: LIGHT-EMITTING-DIODES
EFFICIENT ENERGY-TRANSFER
EMISSION-TUNABLE PHOSPHOR
EXCITED WHITE LEDS
CRYSTAL-STRUCTURE
LUMINESCENCE PROPERTIES
Mn2+ PHOSPHOR
COLOR TONE
PHASE
Eu2+
Аннотация: Cation substitution dependent tunable bimodal photoluminescence behavior was observed in the Ca3-xSrx(PO4)2:Eu2+ (0 ≤ x ≤ 2) solid solution phosphors. The Rietveld refinements verified the phase purity and whitlockite type crystal structure of the solid solutions. The tunable photoluminescence evolution was studied as a function of strontium content, over the composition range 0.1 ≤ x ≤ 2. In addition to the emission band peak at 416 nm in Ca3(PO4)2:Eu2+, the substitution of Ca2+ by Sr2+ induced the emerging broad-band peak at 493-532 nm. A dramatic red shift of the emission peak located in the green-yellow region was observed on an increase of x in the samples with 0.75 ≤ x ≤ 2.00. The two emission bands could be related to the EuOn-Ca9 and EuOn-Ca9-xSrx emitting blocks, respectively. The values for the two kinds of emitting blocks in the solid solutions can be fitted well with the observed intensity evolution of the two emission peaks.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang, Qiuhong, Li, Junhao, Jiang, Wei, Lin, Litian, Ding, Jianhong, Brik, Mikhail G., Molokeev M. S., Ni, Haiyong, Wu, Mingmei
Заглавие : CaY2Al4SiO12:Ce3+,Mn2+: a single component phosphor to produce high color rendering index WLEDs with a blue chip
Место публикации : J. Mater. Chem. C. - 2021. - Vol. 9, Is. 34. - P.11292-11298. - ISSN 2050-7526, DOI 10.1039/d1tc01770e. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 35. - This work has been financially supported by the National Nature Science Foundation of China (51902063, 51902354, U1801253), the Science and Technology Project of Guangdong Province (2018A050506061), the Science and Technology Project of Guangzhou City (202007020005, 202007020008) and GDAS' Project of Science and Technology Development (2020GDASYL-20200302010, 2018GDASCX-0110). M. G. Brik also thanks the support from the Chongqing Recruitment Program for 100 Overseas Innovative Talents (Grant No. 2015013), the Program for the Foreign Experts (Grant No. W2017011) and Wenfeng High-End Talents Project (Grant No. W2016-01) offered by Chongqing University of Posts and Telecommunications (CQUPT), Estonian Research Council grant PUT PRG111, European Regional Development Fund (TK141) and NCN project 2018/31/B/ST4/00924
Предметные рубрики: GARNET PHOSPHOR
ENERGY-TRANSFER
RED EMISSION
LUMINESCENCE PROPERTIES
Аннотация: A high color rendering index white light emitting diode (WLED) is generally produced by combining yellow and red mixed phosphors on a blue chip. Herein we report a single component phosphor based on CaY2Al4SiO12 (CYAS) to achieve warm white light emission with a high color rendering index (Ra), which can be up to 90.5. Ce3+, Mn2+ singly doped and co-doped CYAS phosphors have been synthesized by solid state reactions, respectively, for comparative investigations. The Rietveld X-ray diffraction (XRD) refinements show that the CYAS host crystallizes in a cubic structure with the Ia[3 with combining macron]d space group. The valence states of Ce and Mn inside the CYAS host have been confirmed by XPS and EPR. Ce3+ occupies the Ca2+/Y3+ site and generates a yellow emission band around 543 nm from its characteristic 5d–4f transition. Mn2+ occupies both the dodecahedron Ca2+/Y3+ and octahedral Al3+ sites, emitting red and deep red lights at 616 nm and 750 nm, respectively. These two emission bands are attributed to the 4T1(4G)–6A1(6S) transitions of Mn2+. Upon 460 nm light excitation, both the Ce3+ and Mn2+ characteristic emissions can be obtained, in which the emissions of Mn2+ result from the occurrence of energy transfer from Ce3+ in CYAS. All the results indicate that the prepared CYAS:Ce3+,Mn2+ could be a promising single component phosphor for blue chip WLEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Guo Q., Liao L., Molokeev M. S., Mei L., Liu H.
Заглавие : Color tunable emission and energy transfer of Ce3+ and Tb3+ co-doped novel La6Sr4(SiO4)6F2 phosphors with apatite structure
Место публикации : Mater. Res. Bull.: Elsevier, 2015. - Vol. 72. - P.245-251. - ISSN 0025-5408, DOI 10.1016/j.materresbull.2015.07.029
Примечания : Cited References: 37. - This present work is supported by the National Natural Science Foundations of China (Grant No. 41172053).
Предметные рубрики: LIGHT-EMITTING-DIODES
LUMINESCENCE PROPERTIES
PHOTOLUMINESCENCE PROPERTIES
EU2+
LEDS
Ключевые слова (''Своб.индексиров.''): inorganic compounds--luminescence--phosphors--optical properties--crystal structure
Аннотация: Single-phase La6Sr4(SiO4)6F2: Ce3+, Tb3+ samples with apatite-like structure have been synthesized via solid-state reaction method. The phase structure, luminescence properties, lifetime, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples. Effective energy transfer occurs from Ce3+ to Tb3+ in La6Sr4(SiO4)6F2, which shows more intense Blue-Green light under UV light excitation. In addition, a possible mechanism of the energy-transfer from Ce3+ to Tb3+ ion is also proposed. The critical distance RC of Ce3+ to Tb3+ ions in La6Sr4(SiO4)6F2 host was calculated to be 11.878 Å. All the results indicate that La6Sr4(SiO4)6F2:Ce3+, Tb3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes. © 2015 Elsevier Ltd. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ma, Bin, Guo Q. F., Molokeev M. S., Lv, Zhenfei, Yao, Jun, Mei, Lefu, Huang, Zhaohui
Заглавие : Crystal structure and luminescence properties of green-emitting Sr1−xAl12O19:xEu2+ phosphors
Место публикации : Ceram. Int.: Elsevier Science, 2016. - Vol. 42, Is. 5. - P.5995-5999. - ISSN 0272-8842, DOI 10.1016/j.ceramint.2015.12.149. - ISSN 1873-3956(eISSN)
Примечания : Cited References: 30. - This work was supported by the National Natural Science Foundation of China (Grant nos. 51032007 and 51372232) and the Fundamental Research Funds for the Central Universities (Grant no. 2652015024).
Предметные рубрики: COLOR-TUNABLE PHOSPHOR
ENERGY-TRANSFER
Dy3+ PHOSPHORS
NEAR-UV
Eu2+
DIODES
PHASE
STATE
Ce3+
Ключевые слова (''Своб.индексиров.''): crystal structure--magnetoplumbite--phosphor
Аннотация: In this paper, a series of novel luminescent Sr1−xAl12O19:xEu2+ phosphors were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the decay curves were investigated. The quenching concentration of Eu2+ in SrAl12O19 was about 0.15 (mol). Upon excitation at 378 nm, the composition-optimized Sr0.85Al12O19:0.15Eu2+ exhibited strong broad-band green emission at 530 nm with the CIE chromaticity (0.2917, 0.5736). The results indicate that Sr1−xAl12O19:xEu2+ phosphors have potential applications as green-emitting phosphors for UV-pumped white-light LEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia Y., Chen J., Liu Y.-G., Molokeev M. S., Guan M., Huang Z., Fang M.
Заглавие : Crystal structure evolution and luminescence properties of color tunable solid solution phosphors Ca2+xLa8-x(SiO4)6-x(PO4)xO2:Eu2+
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2016. - Vol. 45, Is. 3. - P.1007-1015. - ISSN 14779226 (ISSN), DOI 10.1039/c5dt03786g
Примечания : Cited References: 42. - This work was sponsored by National Natural Science Foundation of China (Grant No. 51472223), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-12-0951) and the Fundamental Research Funds for the Central Universities (Grant No. 2652015020).
Предметные рубрики: LIGHT-EMITTING-DIODES
WHITE-LIGHT
ENERGY-TRANSFER
SILICATE GLASS
SINGLE-PHASE
EU2+
LEDS
PHOTOLUMINESCENCE
EMISSION
UV
Аннотация: A series of apatite solid solution phosphors Ca2+xLa8-x(SiO4)6-x(PO4)xO2:Eu2+ (x = 0,2,4,6) were synthesized by a conventional higherature solid-state reaction. The phase purity was examined using XRD, XPS and XRF. The crystal structure information, such as the concentration, cell parameters and occupation rate, was analyzed using a Rietveld refinement, demonstrating that the Eu2+ activated the Ca2La8(SiO4)6O2 and Ca8La2(PO4)6O2 to form continuous solid solution phosphors. Different behaviors of luminescence evolution in response to structural variation were verified among the series of phosphors. Two kinds of Eu2+ ion sites were proved using low temperature PL spectra (8k) and room temperature decay curves. The substitution of large La3+ ions by small Ca2+ ions induced a decreased crystal field splitting of the Eu2+ ions, which caused an increase in emission energy from the 5d excited state to the 4f ground state and a resultant blue-shift from 508 nm to 460 nm. Therefore, with the crystal structure evolution, the emitted color of the series of phosphors could be tuned from green to blue by adjusting the ratio of Ca/La. © 2016 The Royal Society of Chemistry.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Miao, Shihai, Xia, Zhiguo, Molokeev M. S., Chen, Mingyue, Zhang, Jie, Liu, Quanlin
Заглавие : Effect of Al/Si substitution on the structure and luminescence properties of CaSrSiO4:Ce3+ phosphors: analysis based on the polyhedra distortion
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2015. - Vol. 3, Is. 18. - P.4616-4622. - ISSN 2050, DOI 10.1039/c5tc00339c. - ISSN 20507534(eISSN)
Примечания : Cited References:30. - The present work was supported by the National Natural Science Foundations of China (Grant No. 51002146, 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635), the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306) and the excellent tutor section of the Fundamental Research Funds for the Central Universities of China University of Geosciences, Beijing (2652015027).Cover image: Artwork representing main idea of this article
Предметные рубрики: LIGHT-EMITTING-DIODES
COLOR-TUNABLE PHOSPHOR
ENERGY-TRANSFER
Аннотация: Blue-emitting CaSrSiO4:Ce3+,Li+ phosphors were prepared by a high temperature solid-state method, and the effect of substituting Al3+ for Si4+ in CaSrSiO4:Ce3+,Li+ has been studied. Crystal structures of the as-prepared Ca1−ySr1−ySi1−xAlxO4:yCe3+,yLi+ phosphors were resolved by the Rietveld method, which suggested that all the samples belonged to the orthorhombic symmetry (Pnma) group of α-CaSrSiO4. The photoluminescence (PL) emission and excitation spectra, the lifetime, and the effect of Al3+ concentration on the PL properties were investigated in detail. The emission peaks of the CaSrSi1−xAlxO4:Ce3+,Li+ (x = 0–0.10) phosphors were red-shifted from 452 to 472 nm with increasing Al/Si ratio. The red-shift of the Ce3+ emission is ascribed to the polyhedra distortion of the cations, originating from the variation in the neighboring [(Si,Al)O4] polyhedra, and the detailed mechanism has been discussed.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhao, Ming, Liao, Hongxu, Molokeev M. S., Zhou, Yayun, Zhang, Qinyuan, Liu, Quanlin, Xia, Zhiguo
Заглавие : Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition
Место публикации : Light: Sci. Appl. - 2019. - Vol. 8. - Ст.38. - ISSN 2047-7538, DOI 10.1038/s41377-019-0148-8
Примечания : Cited References: 31. - The present work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 51572023 and 91622125), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and the Guangdong Provincial Science & Technology Project (No. 2018A050506004). M.S.M. is grateful for the support from the Russian Foundation for Basic Research (Grant No. 17-52-53031).
Предметные рубрики: LUMINESCENCE PROPERTIES
TEMPERATURE
ROUTE
Аннотация: Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials. The discovery of cyan-emitting (470–500 nm) phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light. Na0.5K0.5Li3SiO4:Eu2+ (NKLSO:Eu2+) phosphor was developed with impressive properties, providing cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C. The ultra-narrow-band cyan emission results from the high-symmetry cation sites, leading to almost ideal cubic coordination for UCr4C4-type compounds. NKLSO:Eu2+ phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled, and the color-rendering index can be enhanced from 86 to 95.2, suggesting great applications in full-spectrum white LEDs.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Deng J., Zhang H., Zhang X., Molokeev M. S., Qiu J., Liu Y., Lei B., Ma L., Wang X.
Заглавие : Enhanced luminescence performance of CaO:Ce3+,Li+,F- phosphor and its phosphor-in-glass based high-power warm LED properties
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4077-4086. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00813b
Примечания : Cited References: 44. - The present study was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), the Guangzhou Science & Technology Project (No. 201704030086) and the Open Project Fund from Key Laboratory of Advanced of Materials of Yunnan Province (No. 2018KF01).
Ключевые слова (''Своб.индексиров.''): correlated color temperature--critical concentration--doping concentration--enhanced luminescence--high color rendering index--high power white led--high temperature solid-state reaction--thermal and chemical stabilities
Аннотация: To obtain white light-emitted diodes (wLEDs) with a low correlated color temperature (CCT) and a high color rendering index (CRI), red-emission is indispensable in their emission spectra. Herein, CaO:Ce3+,Li+,F- yellow phosphors with more red spectral component have been prepared via a high temperature solid-state reaction. As compared to the F- undoped samples, CaO:Ce3+,Li+,F- phosphor have lower critical doping concentration of Ce3+ and show stronger luminescence. At the critical concentration, a quantum efficiency of 66.4% and enhanced thermal and chemical stability were obtained in CaO:Ce3+,Li+,F-. Furthermore, a CaO:Ce3+,Li+,F--based phosphor-in-glass (PiG) using the red-emitting glass system with the composition of SiO2-Na2CO3-Al2O3-CaO:Eu3+ as the host material was constructed and used for high-power white LED applications. Such PiG samples with different phosphor doping concentrations can satisfy various light color demands and display higher reliability than the CaO:Ce3+,Li+,F- phosphor. An optimal PiG-based wLED exhibits color coordinates of (0.3769, 0.3386), a CCT of 3774 K, a CRI of 82.5 and a LE of 73.1 when the mass ratio of phosphor to glass matrix was 7:50 in PiG. Moreover, such PiG-based wLED also showed acceptable color stability under different drive currents. All the above results demonstrate that CaO:Ce3+,Li+,F- can be expected to be a potential alternative yellow phosphor for blue light excited PiG based warm wLEDs, particularly for high-power devices.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yan W., Wei Y., Molokeev M. S., Wang S., Li G.
Заглавие : Green-emitting Bi3+-doped La2SrSc2O7 phosphor for pc-WLED lighting: Luminescent properties and energy transfer strategy
Место публикации : J. Alloys Compd. - 2022. - Vol. 908. - Ст.164621. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2022.164621
Примечания : Cited References: 63. - This work was supported by the National Natural Science Foundation of China (Grant Nos. 52072349)
Аннотация: The crystal structure, photoluminescence properties, thermal stability and corresponding mechanisms of the novel Bi3+, Eu3+-doped La2SrSc2O7 (LSS) phosphors have been measured and analyzed in details. The emission spectrum of LSS: 1.0%Bi3+ phosphor shows a novel green emission centered at 530 nm under 340 nm excitation, which is attributed to the 3P1→1S0 transition of Bi3+ ions. By designing Bi3+→Eu3+energy transfer strategy, luminescence colors of LSS: 1.0%Bi3+, yEu3+ (y = 0–5.0%) phosphors can be tuned from green to orange with increasing Eu3+ concentration, which achieve multiple emission colors in LSS host. The photoluminescence decay curves, average decay lifetimes, energy transfer efficiency and time-resolved emission spectra of LSS: 1.0%Bi3+, yEu3+ (y = 0–5.0%) phosphors prove the existence of energy transfer from Bi3+ to Eu3+. The prototype pc-WLED device with green-emitting LSS: 1.0%Bi3+ possesses high color rendering index (CRI = 96.0) and low correlated color temperature (CCT = 4306 K). These results provide clear evidences that LSS: Bi3+and LSS: 1.0%Bi3+, Eu3+ phosphors would be novel promising green-to-orange tunable phosphor candidates for pc-WLED applications.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hsiao, Yu-Cheng, Timofeev I. V., Zyryanov V. Ya., Lee, Wei
Заглавие : Hybrid anchoring for a color-reflective dual-frequency cholesteric liquid crystal device switched by low voltages
Коллективы : Ministry of Science and Technology, Taiwan [103-2923-M-009-003-MY3]; Russian Foundation for Basic Research [14-02-31248]; Siberian Branch of the Russian Academy of Sciences (SB RAS) through an NSC-SB-RAS joint project between Taiwan and Russia
Место публикации : Opt. Mater. Express: Optical Society of America, 2015. - Vol. 5, Is. 11. - P.2715-2720. - ISSN 2159-3930, DOI 10.1364/OME.5.002715
Примечания : Cited References:17. - This work was financially sponsored by the Ministry of Science and Technology, Taiwan, under grant No. 103-2923-M-009-003-MY3, by the Russian Foundation for Basic Research (project No. 14-02-31248), and by the Siberian Branch of the Russian Academy of Sciences (SB RAS) through an NSC-SB-RAS joint project between Taiwan and Russia
Предметные рубрики: Photonic structure
Drive scheme
Modulation
Аннотация: Cholesteric liquid crystal (CLC) materials used in electro-optical (EO) devices are characterized by high operating voltage and slow response speed, which hinders their further development in display applications. Dual-frequency CLCs (DFCLCs) can solve the problem of slow bistable transition, but the operating voltage is still high, especially in color-reflective DFCLC cells. Here we report a simple approach to lowering the switching voltage as well as to shortening the response time. This technique adopts hybrid surface treatment to modulate the structural arrangement of CLC molecules. Both planar-and vertical-alignment layers are employed and coated on one and the other substrates separately to improve the electro-optical properties of DFCLCs. We show that the threshold voltage for switching can be decreased to as low as 5 V and the shortest response time is measured to be 0.8 ms, which renders CLC EO devices including displays more practical for commercial purpose.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang X., Li J. -G., Molokeev M. S., Zhu Q., Li X., Sun X.
Заглавие : Layered hydroxyl sulfate: Controlled crystallization, structure analysis, and green derivation of multi-color luminescent (La,RE)2O2SO4 and (La,RE)2O2S phosphors (RE = Pr, Sm, Eu, Tb, and Dy)
Место публикации : Chem. Eng. J.: Elsevier, 2016. - Vol. 302. - P.577-586. - ISSN 13858947 (ISSN), DOI 10.1016/j.cej.2016.05.089
Примечания : Cited References: 50. - This work is supported in part by the National Natural Science Foundation of China (Grants Nos. 51172038, 51302032, and U1302272), the Fundamental Research Fund for the Central Universities (Grant No. N140204002), Grants-in-Aid for Scientific Research (KAKENHI No. 26420686), and the Russian Foundation for Basic Research (15-52-53080). X.J. Wang acknowledges financial support from the China Scholarship Council for her overseas Ph.D. study (Contract No. 201406080035) and the assistance of Q. Q. Zhu (University of Science and Technology of China) for his help with calcination.
Предметные рубрики: PHOTOLUMINESCENCE PROPERTIES
OXYSULFATE/OXYSULFIDE SYSTEMS
CRYSTAL-STRUCTURE
OXYGEN-STORAGE
Ln
NANOCOMPOSITES
EMISSION
CAPACITY
FAMILY
FABRICATION
Ключевые слова (''Своб.индексиров.''): sulfate type layered rare earth hydroxide--luminescence--oxysulfate--oxysulfide
Аннотация: The two important groups of Ln2O2SO4 and Ln2O2S compounds are traditionally synthesized with the involvements of environmentally harmful sulfur-containing reagents. We developed in this work a unique green approach for their synthesis, using Ln2(OH)4SO4·2H2O layered hydroxyl sulfate as the precursor (Ln-241 phase). Phase selective crystallization of La-241 under both atmospheric pressure and hydrothermal conditions was firstly optimized, followed by transformation into La2O2S and La2O2SO4 by controlled calcination. Rietveld structure refinement was performed for La-241, La(OH)SO4, La2O2SO4, and La2O2S, and the crystal structure and cell parameters of La-241 were originally reported. The photoluminescence performances of several important activators (Pr3+, Sm3+, Eu3+, Tb3+, and Dy3+) in the two hosts, in terms of excitation, emission, quantum yield, and color coordinates of emission, were thoroughly investigated, and multi-color luminescence including bright red, green, orange red, and yellow was obtained under ultraviolet excitation. Detailed investigations of Tb3+ photoluminescence revealed that the lack of 5D3 emission in La2O2S and the gradual quenching of 5D3 blue emission at a higher Tb3+ content (hence decreasing I488/I545 ratio and changing color coordinates) in La2O2SO4 were suggested to be due to thermal activation of the 5D3 electrons into the conduction band and cross relaxation between adjacent Tb3+, respectively. The synthesis approach developed in this work for La2O2SO4 and La2O2S, with water vapor as the only exhaust gas, is environmentally benign and holds great potential in the facile synthesis of analogous compounds of other lanthanides. © 2016 Elsevier B.V.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liao, Hongxu, Zhao, Ming, Molokeev M. S., Liu, Quanlin, Xia, Zhiguo
Заглавие : Learning from a mineral structure toward an ultra-narrow-band blue-emitting silicate phosphor RbNa3(Li3SiO4)4:Eu2+
Место публикации : Angew. Chem. - Int. Edit. - 2018. - Vol. 57, Is. 36. - P.11728-11731. - ISSN 1433-7851, DOI 10.1002/anie.201807087. - ISSN 1521-3773(eISSN)
Примечания : Cited References: 22. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 91622125 and 51572023), and Natural Science Foundations of Beijing (2172036), and M.S.M. acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Предметные рубрики: RED PHOSPHORS
COLOR-GAMUT
LUMINESCENCE
Ключевые слова (''Своб.индексиров.''): luminescence--minerals--phosphors--rigid structure--silicates
Аннотация: Learning from natural mineral structures is an efficient way to develop potential host lattices for applications in phosphor converted (pc)LEDs. A narrow‐band blue‐emitting silicate phosphor, RbNa3(Li3SiO4)4:Eu2+ (RNLSO:Eu2+), was derived from the UCr4C4‐type mineral model. The broad excitation spectrum (320–440 nm) indicates this phosphor can be well matched with the near ultraviolet (n‐UV) LED chip. Owing to the UCr4C4‐type highly condensed and rigid framework, RNLSO:Eu2+ exhibits an extremely small Stokes shift and an unprecedented ultra‐narrow (full‐width at half‐maximum, FWHM=22.4 nm) blue emission band (λem=471 nm) as well as excellent thermal stability (96 %@150 °C of the initial integrated intensity at 25 °C). The color gamut of the as‐fabricated (pc)LEDs is 75 % NTSC for the application in liquid crystal displays from the prototype design of an n‐UV LED chip and the narrow‐band RNLSO:Eu2+ (blue), β‐SiAlON:Eu2+ (green), and K2SiF6:Mn4+ (red) components as RGB emitters.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang, Xuejiao, Feng, Xiaowen, Molokeev M. S., Zheng, Huiling, Wang, Qiushi, Xu, Chunyan, Li, Ji-Guang
Заглавие : Modulation of Bi3+ luminescence from broadband green to broadband deep red in Lu2WO6 by Gd3+ doping and its applications in high color rendering index white LED and near-infrared LED
Место публикации : Dalton Trans. - 2023. - Vol. 52, Is. 9. - P.2619-2630. - ISSN 14779226 (ISSN), DOI 10.1039/D2DT03751C. - ISSN 14779234 (eISSN)
Примечания : Cited References: 4. - This work is supported in part by the Project of Education Department of Liaoning Province (Grant No. LQ2019014) and he Natural Science Foundation of Liaoning Province (Grant No. 2020-MS-286). The authors are thankful for the support for the 4B9A Beamline from the Beijing Synchrotron Radiation Facility (BSRF) (Project No. 2021-BEPC-PT-005290). The authors would like to thank Siqi Liu from Shiyanjia Lab (
Аннотация: Phosphors that exhibit tunable broadband emissions are highly desired in multi-functional LEDs, including pc-WLEDs and pc-NIR LEDs. In this work, broadband emissions were obtained and modulated in the unexpectedly wide spectral range of 517–609 nm for (Lu0.99−xGdxBi0.01)2WO6 phosphors by tuning the Gd3+ content (x = 0–0.99). The effects of Gd3+ doping on phase constituents, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained from Gd3+-free (Lu0.99Bi0.01)2WO6 phosphors (x = 0), whose emission intensity was enhanced by 50% with 5 at% Gd3+ (x = 0.05). The phase transition happened when x 0.50 and the broadband red-NIR emission was obtained when x = 0.75–0.99. Three luminescence centers were proved to be responsible for the broadband green emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with a high color rendering index (Ra = 91.3), a stable emission color, and a low color temperature (3951 K) was fabricated from the (Lu0.94Gd0.05Bi0.01)2WO6 broadband green phosphor, and an LED device that simultaneously emits high color rendering index white light and NIR light was obtained with the (Gd0.99Bi0.01)2WO6 broadband red-NIR phosphor. Night vision and noninvasive imaging were also demonstrated using the latter LED device.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu C., Xia, Zhiguo, Chen M., Molokeev M. S., Liu Q.
Заглавие : Near-infrared luminescence and color tunable chromophores based on Cr3+-Doped Mullite-Type Bi2(Ga,Al)4O9 solid solutions
Место публикации : Inorg. Chem.: American Chemical Society, 2015. - Vol. 54, Is. 4. - P.1876-1882. - ISSN 0020-1669, DOI 10.1021/ic502779d
Примечания : Cited References: 26. - The present work was supported by the National Natural Science Foundations of China (Grants 51002146, 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635), the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306), and Fundamental Research Funds for the Central Universities (FRF-TP-14-005A1).
Предметные рубрики: PERSISTENT LUMINESCENCE
PHOSPHORS
PIGMENT
GARNET
OXIDES
FIELD
RED
Аннотация: Cr3+-activated mullite-type Bi2Ga(4-x)AlxO9 (x = 0, 1, 2, 3, and 4) solid solutions were prepared by the solid state reaction, and their spectroscopic properties were investigated in conjunction with the structural evolution. Under excitation at 610 nm, Bi2[Ga(4-y)Aly]3.97O9:0.03Cr3+ (y = 0, 1, 2, 3, and 4) phosphors exhibited broad-band near-infrared (NIR) emission peaking at ?710 nm in the range 650?850 nm, and the optimum Cr3+ concentrations and concentration quenching mechanism were determined. Except for the interesting NIR emission, the body color changed from white (at x = 0) to green (at x = 0.08) for Bi2Ga4?xO9:xCr3+, and from light yellow (at x = 0) to deep brown (at x = 0.08) for Bi2Al4?xO9:xCr3+, respectively. Moreover, as a result of variable Al/Ga ratio, the observed body color for Bi2[Ga(4-y)Aly]3.97O9:0.03Cr3+ (y = 0, 1, 2, 3, and 4) varied from deep brown to green. The relationship between the observed colors and their diffuse reflectance spectra were also studied for the understanding of the different absorption bands. The results indicated that Cr3+-doped Bi2Ga(4-x)AlxO9 solid solutions appeared as the bifunctional materials with NIR phosphors and color-tunable pigments.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Arkhipkin V. G., Bezmaternykh L. N., Gudim I. A., Krylov A. S., Vagizov F.
Заглавие : Origin of color centers in the flux-grown europium gallium garnet
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 103, Is. 8. - Ст.83102. - ISSN 0021-8979, DOI 10.1063/1.2902365
Примечания : Cited References: 7
Предметные рубрики: SPECTRA
IONS
Ключевые слова (''Своб.индексиров.''): absorption--europium alloys--garnets--ultraviolet radiation--calcium-free flux--flux-grown europium gallium garnet--color centers
Аннотация: Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Mossbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Mossbauer isotope shifts and quadrupole splitting for EuGG are determined. (C) 2008 American Institute of Physics.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pustovarov V. A., Ogorodnikov I. N., Omelkov S. I., Molokeev M. S., Kozlov A. V., Isaenko L. I.
Заглавие : Photoluminescence of monoclinic Li3AlF6 crystals under vacuum ultraviolet and soft X-ray excitations
Место публикации : Opt. Mater.: Elsevier, 2015. - Vol. 49. - P.201-207. - ISSN 0925-3467, DOI 10.1016/j.optmat.2015.09.011
Примечания : Cited References: 49. - This work was partly supported by the Ministry of Education and Science of the Russian Federation (the basic part of the government mandate); Center of Excellence "Radiation and Nuclear Technologies" (Competitiveness Enhancement Program of Ural Federal University, Russia), HASYLAB DESY (Projects Nos. 20110843, 20080119EC), European Social Fund ("Mobilitas" program, MJD219), Estonian Research Council (Institutional Research Funding IUT02-26) and Baltic Science Link project coordinated by the Swedish Research Council, VR
Предметные рубрики: LiBaAlF6 single-crystals
F-type centers
LiBaF3 crystals
Color-centers
Recombination luminescence
Rietveld refinement
VUV spectroscopy
Trapped excitons
Energy-transfer
Pure
Ключевые слова (''Своб.индексиров.''): li3alf6--time-resolved luminescence--vuv spectroscopy--defects
Аннотация: Using Bridgman technique we have grown monoclinic β-LiAF crystals suitable for optical studies, performed XRD-identification and Rietveld refinement of the crystal structure and carried out a photoluminescence study upon vacuum ultraviolet (VUV) and extreme ultraviolet (XUV)-excitations, using the low-temperature (T = 7.2 K) time-resolved VUV-spectroscopy technique. The intrinsic PL emission band at 340–350 nm has been identified as due to radiative recombination of self-trapped excitons. The electronic structure parameters were determined: bandgap E g ≈ 12.5 eV, energy threshold for creation of unrelaxed excitons 11.8 eV < E n < 12.5 eV . The PL emission bands at 320–325 and 450 nm were attributed to luminescence caused by lattice defects. We have discovered an efficient excitation of PL emission bands in the energy range of interband transitions ( E ex > 13.5 eV), as well as in the energy range of core transitions at 130 eV. We have revealed UV–VUV PL emission bands at 170 and 208 nm due to defects. A reasonable assumptions about the origin of the UV–VUV bands were discussed.
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