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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen Y., Liu F., Zhang Z., Hong J., Molokeev M. S., Bobrikov I. A., Shi J., Zhou J., Wu M.
Заглавие : A novel Mn4+-activated fluoride red phosphor Cs30(Nb2O2F9)9(OH)3·H2O:Mn4+ with good waterproof stability for WLEDs
Место публикации : J. Mater. Chem. C. - 2022. - Vol. 10, Is. 18. - P.7049-7057. - ISSN 20507534 (ISSN), DOI 10.1039/d2tc00132b
Примечания : Cited References: 56. - This work was financially supported by grants from the National Natural Science Foundation of China (NSFC) (No. 51802359), the Joint Funds of NSFC and Yunnan Province (No. U1702254), and Guangdong Basic and Applied Basic Research Foundation (No. 2020A1515010556)
Аннотация: Red-light-emitting materials, as pivotal components of warm white light-emitting diodes (WLEDs), have drawn increasing public focus. Among these, Mn4+-doped red light-emitting fluorides have drawn considerable attention when combined with an InGaN chip; however, they suffer from poor water stability under humid conditions. In this work, a novel fluoride red phosphor, Cs30(Nb2O2F9)9(OH)3·H2O:xMn4+ (CNOFM), with good water resistance was synthesized for the first time using a facile co-precipitation method at ambient temperature. Experiments were implemented for the precise analysis of its crystal structure, optical properties, micro-morphology, thermal behavior, and waterproof properties. 6.66% Mn4+-doped CNOFM maintained a stable crystal structure and possessed strong PL intensity located at 633 nm with high color purity of 96%. CNOFM showed better thermal and waterproof stability compared with the commercial K2SiF6:Mn4+ red phosphor. Without any surface modifications, the PL intensity remained at about 83% of the initial value after immersion in water for 60 min, and the mechanism was investigated. Finally, a warm WLED with a CRI of 92.3 and CCT of 3271 K was fabricated using the CNOFM red phosphor.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xing, Gongcheng, Feng, Yuxin, Gao, Zhiyu, Tao, Mengxuan, Wang, Hongquan, Wei, Y.i., Molokeev M. S., Li, Guogang
Заглавие : A novel red-emitting La2CaHfO6:Mn4+ phosphor based on double perovskite structure for pc-WLEDs lighting
Место публикации : CrystEngComm. - 2019. - Vol. 21, Is. 23. - P.3605-3612. - ISSN 1466-8033, DOI 10.1039/c9ce00556k
Примечания : Cited References: 47. - This work is financially supported by the National Natural Science Foundation of China (NSFC No. 51672259).
Предметные рубрики: LUMINESCENCE PROPERTIES
ELECTRONIC-STRUCTURE
OPTICAL-PROPERTIES
SITE
Аннотация: Non-rare earth doped oxides with red emission are one of the current research hotspots for achieving the warm white light range in the phosphor converted white light emitting diodes (pc-WLEDs) field. In the current work, a novel Mn4+-activated La2CaHfO6 red phosphor is reported for the first time and its crystal structure is analyzed by Rietveld refinement. The photoluminescent properties of La2CaHfO6:Mn4+ are investigated in detail with the help of diffuse refletance spectroscopy, photoluminescence spectroscopy, and temperature-dependent PL spectroscopy. Based on the diffuse refletance spectra, the calculated optical band gap for La2CaHfO6 is 4.9 eV, indicating that La2CaHfO6 could be a suitable host for activators' doping. Under 380 nm near-ultraviolet (n-UV) light excitation, the as-prepared La2CaHfO6:Mn4+ displays intense red emission centered at 693 nm. Through an accurate calculation of Dq/B (2.47) and nephelauxetic effect β1 (0.949), the origination of strong crystal field (CF) and deep-red emission is demonstrated. By combining the representative La2CaHfO6:0.002Mn4+, blue BAM:Eu2+, and green (Ba,Sr)2SiO4:Eu2+ phosphors with a 380 nm UV chip to fabricate the pc-WLEDs device, a white light is obtained with low correlated color temperature (CCT = 5165 K) and high color rendering index (Ra = 87.8), demonstrating that the as-prepared La2CaHfO6:Mn4+ phosphors can be used as red-emitting candidate in pc-WLEDs lighting.
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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) : Zhou J., Chen Y., Jiang C., Milicevic B., Molokeev M. S., Brik M. G., Bobrikov I. A., Yan J., Li J., Wu M.
Заглавие : High moisture resistance of an efficient Mn4+-activated red phosphor Cs2NbOF5:Mn4+ for WLEDs
Место публикации : Chem. Eng. J. - 2021. - Vol. 405. - Ст.126678. - ISSN 13858947 (ISSN), DOI 10.1016/j.cej.2020.126678
Примечания : Cited References: 43. - This work was financially supported by grants from the National Natural Science Foundation of China (No. 51802359, 21801254, 51902354) and its Joint Funds of Yunnan and Guangdong Province (No. U1702254 and No. U1801253), Special Fund of Guangdong Province Project for Applied Science and Technology Research and Development (No. 2017B090917001), Guangdong Basic and Applied Basic Research Foundation (No. 2020A1515010556), the Fundamental Research Funds for the Central Universities (No. 19lgpy123), and China Postdoctoral Science Foundation (No. 2019M663230). M. G. Brik thanks the supports from the National Recruitment Program of High-end Foreign Experts (No. GDT20185200479 and GDW20145200225), the Programme for the Foreign Experts (No. W2017011) and Wenfeng High-end Talents Project (No. W2016-01) offered by Chongqing University of Posts and Telecommunications (CQUPT) , Estonian Research Council grant PUT PRG111, and European Regional Development Fund (TK141)
Аннотация: Mn4+-activated fluoride red phosphors, the most important red phosphors for warm white light emitting diodes (LEDs), usually suffer from inherent poor moisture resistance which is a major obstacle to their long-lasting outdoor applications in a high humidity environment. Surface modification of phosphors by coating with either organic or inorganic shells is an effective way to improve waterproof stability. However, the coating procedure usually has a negative impact on the luminous efficacy due to the increased passivation shell thickness. In this work, Mn4+-activated oxyfluoroniobate (Cs2NbOF5), a highly efficient phosphor with internal quantum efficiency of ca. 82%, has been successfully synthesized and it is interesting to note that Cs2NbOF5:Mn4+ can exhibit remarkably improved waterproof stability even without surface coating compared to well-accepted commercial fluoride red-emitting phosphor, K2SiF6:Mn4+. The results obtained indicate that Nb5+ ions inside red phosphor play a crucial role in improving the water-resistant performance of Mn4+, which provides a new concept for overcoming the downside of their waterproof in humid conditions and maintaining the luminescence efficiency. In the final phase white LEDs with a high luminous efficacy of 174 lm/W (higher than commercial fluoride red phosphors), low correlated color temperature (3164 K) and high color rendering index (Ra = 90 and R9 = 85) have been fabricated using Cs2NbOF5:Mn4+.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang M., Xia Z., Molokeev M. S., Shi L., Liu Q.
Заглавие : New insight into the crystal structure of Sr4Ca(PO4)2SiO4 and the photoluminescence tuning of Sr4Ca(PO4)2SiO4:Ce3+,Na+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2016. - Vol. 4, Is. 38. - P.9078-9084. - ISSN 20507534 (ISSN), DOI 10.1039/c6tc03373c
Примечания : Cited References: 31
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--light emitting diodes--luminescence--phosphate minerals--phosphors--photoluminescence--positive ions--rietveld refinement--tuning--chemical compositions--energy transfer mechanisms--green component--hexagonal cells--luminescence properties--single phase--solid state method--white lightemitting diodes (wleds)--crystal structure
Аннотация: A new single phase based on the substitution of a Sr cation by a Ca cation in the apatite-type Sr5(PO4)2(SiO4) has been fabricated with the nominal chemical composition of Sr4Ca(PO4)2(SiO4), which appears as a definite compound rather than a solid solution between (Sr,Ca)3(PO4)2 and (Sr,Ca)2SiO4. The crystal structure of Sr4Ca(PO4)2(SiO4) has been firstly analysed by the difference electron map, and further resolved by the Rietveld refinement, and the final composition has been determined as Sr4Ca(PO4)(2+x)(SiO4)(1-x)(OH)x (x = 0.64) with a hexagonal cell (P63/m). The Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been designed and prepared by the solid state method, and the photoluminescence tuning from blue to green upon 365 nm ultraviolet (UV) radiation can be realized, which is ascribed to the energy transfer from Ce3+ to Eu2+ ions. The luminescence properties and the energy transfer mechanism in Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been discussed, which might act as potential candidates for blue-green components in UV-pumped white light emitting diodes (WLEDs). © 2016 The Royal Society of Chemistry.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Han J., Pan F., Molokeev M. S., Dai J., Peng M., Zhou W., Wang J.
Заглавие : Redefinition of crystal structure and Bi3+ yellow luminescence with strong near-ultraviolet excitation in La3BWO9:Bi3+ phosphor for white light-emitting diodes
Место публикации : ACS Appl. Mater. Interfaces. - 2018. - Vol. 10, Is. 16. - P.13660-13668. - ISSN 19448244 (ISSN), DOI 10.1021/acsami.8b00808
Примечания : Cited References: 40
Ключевые слова (''Своб.индексиров.''): bi3+ luminescence--borotungstates--crystal structure--wleds--x-ray diffraction--yellow phosphor
Аннотация: Bi3+-activated photonic materials have received increased interest recently because they can be excited effectively with near-ultraviolet (NUV) but not visible light, thereby avoiding the reabsorption among phosphors, which cannot be solved intrinsically by traditional rare earth (e.g., Eu2+, Ce3+) phosphors. Such unique property suggests their potential application in NUV chip-based WLEDs. However, few Bi3+ phosphors exhibit strong excitation peak in NUV, though the excitation tail of some can extend to NUV. Herein, we report a novel yellow-emitting La3BWO9:Bi3+ (LBW:Bi3+) phosphor with strong NUV excitation. The photoluminescence (PL) spectroscopy analysis indicates that there are two Bi3+ luminescent centers in LBW:Bi3+ phosphor, which is clearly in contradiction with the established hexagonal structure of La3BWO9 with P63 space group because only one La site in this structure can accommodate Bi3+ ions. Combining the luminescent properties of Bi3+ with Rietveld refinement, La3BWO9 was redefined as a trigonal structure with the lower space group of P3 in which there are two independent crystallographic La sites. In addition, the rationalization of P3 space group was further confirmed by the finding of the reflection (0001) according to the extinction rule. Therefore, the PL behavior of Bi3+ can act as a complementary tool to determinate the real crystal structure especially when it is hard to distinguish by conventional X-ray diffraction techniques.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wei Y., Lin C. C., Quan Z., Molokeev M. S., Atuchin V. V., Chan T. -S., Liang Y., Lin J., Li G.
Заглавие : Structural evolution induced preferential occupancy of designated cation sites by Eu2+ in M5(Si3O9)2 (M = Sr, Ba, Y, Mn) phosphors
Место публикации : RSC Adv.: Royal Society of Chemistry, 2016. - Vol. 6, Is. 62. - P.57261-57265. - ISSN 20462069 (ISSN), DOI 10.1039/c6ra11681g
Примечания : Cited References: 28. - This project is financially supported by the National Natural Science Foundation of China (Grants No. NSFC 21301162, 21571162, 60977013, 91433110, U1301242, 21221061), the National College Students' Innovative Training Program (Nos. 201510491109, 201610491067, 201610491070), and the Ministry of Science and Technology of Taiwan (No. MOST 104-2917-1-564-060). Zewei Quan acknowledges the funding support (FRG-SUSTC1501A-17) from South University of Science and Technology of China.
Предметные рубрики: LUMINESCENCE PROPERTIES
RED LUMINESCENCE
UP-CONVERSION
WHITE LEDS
PHOTOLUMINESCENCE
NANOPHOSPHORS
YELLOW
WLEDS
Аннотация: In this paper, we present new insight into a changing Eu2+ crystallographic site preference in Eu-doped M5(Si3O9)2 (M = Sr, Ba, Y, Mn), which is related to the structural variation induced by M cation substitutions. The effect of the local structural geometry on the luminescence properties of Eu2+ is revealed. By substitution of Ba2+ for Sr2+, the lattice expansion is restricted to specific cation sites, resulting in the abrupt blue shifted emission of Eu2+ ions. The abnormal blue shift on replacing Sr2+ with Mn2+ is attributed to the preferential 6-fold coordination for Mn2+ that moves the Eu2+ ions to other sites. The results elucidate the mechanisms of emission band adjustment by local site coordination change and it can be potentially extended to crystals which properties are sensitive to local lattice variations. © 2016 The Royal Society of Chemistry.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wei Y., Qu X., Li G., Cheng Z., Molokeev M. S., Lin C. C., Chan T. -S., Chang C. -K., Chuang Y. -C., Lin J.
Заглавие : Ultra-narrow band blue emission of Eu2+ in halogenated (Alumino)borate systems based on high lattice symmetry
Место публикации : J. Am. Ceram. Soc. - 2019. - Vol. 102. - P.2353– 2369. - ISSN 00027820 (ISSN) , DOI 10.1111/jace.16127
Примечания : Cited References: 63. - This work was supported by the National Natural Science Foundation of China (Grant Nos. 51672259, 51672265, 21521092, 51750110511), Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences (Wuhan) (No. NGM2016KF002), the Ministry of Science and Technology of Taiwan (Contract No. MOST 104-2113-M-027-007-MY3), the Key Research Program of Frontier Sciences, CAS (Grant No. YZDY-SSW-JSC018), and projects for science and technology development plan of Jilin province (20170414003GH), the Program for Jiangmen Innovative Reasearch Team (No.[2017]385),major program of basic research and applied research of Guangdong Province (2017KZDXM083) and the Russian Science Foundation (Grant No. 17-12-01047).
Ключевые слова (''Своб.индексиров.''): blue emission--high symmetry--phosphors--ultra-narrow band--wleds
Аннотация: Phosphor materials with ultra‐high color purity are highly desired in backlit display and WLEDs. How to achieve high‐purity three‐primary emission in rare earth ions activated inorganic phosphors has become a hot topic. Herein, we reported ultra‐narrow band and highly efficient blue‐violet‐emitting Eu2+‐doped Ba2B5O9X (fwhm = 31 nm) and NaBa4(AlB4O9)2X3 (X = Cl, Br) (fwhm = 43 nm) phosphors with peak positions around 424‐437 nm. Especially, the color purity of Ba2B5O9Cl:Eu sample even exceeded 97%, its internal quantum efficiency could achieve 87%. The EXANES analysis revealed that the Eu mainly existed in the form of +2. According to the Rietveld structural refinement, extraordinarily narrow band emission should be attributed to the highly symmetric lattice structures with the flower‐like polyhedrons in the studied (alumino)borate matrix. Significantly, the color gamut of as‐prepared blue phosphor combined with the standard green and red phosphors was almost close to that of Rec. 2020 display standard. In addition, cation substitution strategy in NaBa4(AlxB5‐xO9)2Cl3 (x = 0‐4) and NaBa4(GayB5‐yO9)2Cl3 (y = 0‐3) samples successfully achieved spectra adjustment, and the underlying mechanism was proposed. All these results demonstrate that the as‐prepared phosphors could be superior blue‐emitting candidates for backlit display as well as WLEDs.
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