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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Qiao J., Amachraa M., Molokeev M. S., Chuang Y. -C., Ong S. P., Zhang Q., Xia Z.
Заглавие : Engineering of K3YSi2O7 to Tune Photoluminescence with Selected Activators and Site Occupancy
Место публикации : Chem. Mater. - 2019. - Vol. 31, Is. 18. - P.7770-7778. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.9b02990
Примечания : Cited References: 48. - This work was supported by the National Natural Science Foundation of China (Nos. 51722202, 51972118 and 51572023), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and Guangdong Provincial Science & Technology Project (2018A050506004). This work was also supported by the National Science Foundation, Ceramics Program (No. 1911372), and the computational resources were provided by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation (No. ACI-1548562).
Аннотация: The luminescence of rare earth ions (Eu2+, Ce3+, and Eu3+)-doped inorganic solids is attractive for the screening of phosphors applied in solid-state lighting and displays and significant to probe the occupied crystallographic sites in the lattice also offering new routes to photoluminescence tuning. Here, we report on the discovery of the Eu- and Ce-activated K3YSi2O7 phosphors. K3YSi2O7:Eu is effectively excited by 450 nm InGaN blue light-emitting diodes (LEDs) and displays an orange-red emission originated from characteristic transitions of both Eu2+ and Eu3+, while K3YSi2O7:Ce3+ shows green emission upon 394 nm near-ultraviolet (NUV) light excitation. Rietveld refinement verifies the successful doping of the activators, and density functional theory (DFT) calculations further support that Eu2+ occupies both K1 and Y2 crystallographic sites, while Ce3+ and Eu3+ only occupy the Y2 site; hence, the broad-band red emission of Eu2+ are attributed to a small DFT band gap (3.69 eV) of K3YSi2O7 host and a selective occupancy of Eu2+ in a highly distorted K1 site and a high crystal field splitting around Y2 sites. The white LEDs device utilizing orange-red-emitting K3YSi2O7:Eu and green-emitting K3YSi2O7:Ce3+ exhibits an excellent CRI of 90.1 at a correlated color temperature of 4523 K. Our work aims at bridging multivalent Eu2+/Eu3+ and Ce3+ site occupancy in the same host to realize photoluminescence tuning and especially exposes new ways to explore new phosphors with multicolor emission pumped by blue and NUV light for white LEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lim, Chang Sung, Aleksandrovsky A. S., Atuchin V. V., Molokeev M. S., Oreshonkov A. S.
Заглавие : Microwave sol-gel synthesis, microstructural and spectroscopic properties of scheelite-type ternary molybdate upconversion phosphor NaPbLa(MoO4)3:Er3+/Yb3+
Место публикации : J. Alloys Compd. - 2020. - Vol. 826. - Ст.152095. - ISSN 0925-8388 (ISSN), DOI 10.1016/j.jallcom.2019.152095. - ISSN 1873-4669 (eISSN)
Примечания : Cited References: 53. - This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2018R1D1A1A09082321). This study was supported by the Russian Science Foundation (19-42-02003, in part of conceptualization). Also, this study was supported by RFBR (18-32-20011, 18-03-00750).
Аннотация: New ternary molybdate NaPbLa(1-x-y)(MoO4)3:xEr3+,yYb3+ (x = y = 0, x = 0.05 and y = 0.35, 0.4, 0.45 and 0.5) phosphors were successfully fabricated by the MSG (microwave sol-gel) method, and the microstructural and spectroscopic properties were characterized. The crystal structure of NaPbLa(MoO4)3 (NPLM) was defined by Rietveld analysis in space group I41/a with unit cell parameters a = 5.3735(2) and c = 11.8668(4) Å, V = 342.65(3) Å3, Z = 4 (RB = 6.64%). The unit cell volume of NaPbLa(MoO4)3 (NPLM) was intermediate between those of NaLa(MoO4)2 and PbMoO4. Under the 980 nm excitation, upconverted yellowish-green emissions at transitions from 2H11/2 and 4S3/2 were observed. No concentration quenching in the subsystem of donor ions at the content up to 50 at.% and no cross-relaxation losses in the subsystem of acceptor ions at the concentrations as high as 5 at. % were verified. The individual chromaticity points for the NaPbLa(MoO4)3:Er3+,Yb3+ phosphors, corresponding to the equal-energy point in the standard CIE diagram, revealed yellowish-green emissions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Qiao, Jianwei, Ning, Lixin, Molokeev M. S., Chuang, Yu-Chun, Zhang, Qinyuan, Poeppelmeier, Kenneth R., Xia, Zhiguo
Заглавие : Site-Selective Occupancy of Eu2+ Toward Blue-Light-Excited Red Emission in a Rb3YSi2O7:Eu Phosphor
Место публикации : Angew. Chem. - 2019. - Vol. 131, Is. 33. - P.11645-11650. - ISSN 1521-3757, DOI 10.1002/ange.201905787
Примечания : Cited References: 41. - This work is supported by the National Natural Science Foundation of China (51722202, 51572023, and 11574003), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and the Guangdong Provincial Science & Technology Project (2018A050506004). K.R.P. recognizes that this work was made possible by support from the National Science Foundation, Solid State Materials Chemistry award DMR-1608218.
Предметные рубрики: LUMINESCENCE PROPERTIES
CE3+
ENERGY
PHOTOLUMINESCENCE
TRANSITION
Аннотация: Establishing an effective design principle in solid-state materials for a blue-light-excited Eu2+-doped red-emitting oxide-based phosphors remains one of the significant challenges for white light-emitting diodes (WLEDs). Selective occupation of Eu2+ in inorganic polyhedra with small coordination numbers results in broad-band red emission as a result of enhanced crystal-field splitting of 5d levels. Rb3YSi2O7:Eu exhibits a broad emission band at λmax=622 nm under 450 nm excitation, and structural analysis and DFT calculations support the concept that Eu2+ ions preferably occupy RbO6 and YO6 polyhedra and show the characteristic red emission band of Eu2+. The excellent thermal quenching resistance, high color-rendering index Ra (93), and low CCT (4013 K) of the WLEDs clearly demonstrate that site engineering of rare-earth phosphors is an effective strategy to target tailored optical performance.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fang M. -H., Mahlik S., Lazarowska A., Grinberg M., Molokeev M. S., Sheu H. -S., Lee J. -F., Liu R. -S.
Заглавие : Structural Evolution and Effect of the Neighboring Cation on the Photoluminescence of Sr(LiAl3)1−x(SiMg3)xN4:Eu2+ Phosphors
Место публикации : Angew. Chem. Int. Ed. - 2019. - Vol. 58, Is. 23. - P.7767-7772. - ISSN 14337851 (ISSN), DOI 10.1002/anie.201903178
Примечания : Cited References: 23. - This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 107‐2113‐M‐002‐008‐MY3 and MOST 107–2923‐M‐002‐004‐MY3). This work was supported by the National Science Centre Poland grant Opus no. 2016/23/B/ST3/03911 and the National Centre for Research and Development Poland Grant (No. PL‐TW/V/1/2018).
Предметные рубрики: Solid-Solution Phosphors
Аннотация: In this study, a series of Sr(LiAl3)1−x(SiMg3)xN4:Eu2+ (SLA‐SSM) phosphors were synthesized by a solid‐solution process. The emission peak maxima of SLA‐SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. 7Li solid‐state NMR spectroscopy was utilized to distinguish between the Li(1)N4 and Li(2)N4 tetrahedra in SLA‐SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature‐dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X‐ray absorption near‐edge structure studies reveal that the Eu2+ concentration in SLA‐SSM is much higher than that in in SrLiAl3N4:Eu2+ and SrSiMg3N4:Eu2+ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Qiao, Jianwei, Ning, Lixin, Molokeev M. S., Chuang, Yu-Chun, Zhang, Qinyuan, Poeppelmeier, Kenneth R., Xia, Zhiguo
Заглавие : Site-Selective Occupancy of Eu2+ Toward Blue-Light-Excited Red Emission in a Rb3YSi2O7:Eu Phosphor
Место публикации : Angew. Chem. Int. Edit. - 2019. - Vol. 58, Is. 33. - P.11521-11526. - ISSN 1433-7851, DOI 10.1002/anie.201905787. - ISSN 1521-3773(eISSN)
Примечания : Cited References: 41. - This work is supported by the National Natural Science Foundation of China (51722202, 51572023, and 11574003), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and the Guangdong Provincial Science & Technology Project (2018A050506004). K.R.P. recognizes that this work was made possible by support from the National Science Foundation, Solid State Materials Chemistry award DMR-1608218.
Предметные рубрики: LUMINESCENCE PROPERTIES
CE3+
ENERGY
PHOTOLUMINESCENCE
TRANSITION
Аннотация: Establishing an effective design principle in solid-state materials for a blue-light-excited Eu2+-doped red-emitting oxide-based phosphors remains one of the significant challenges for white light-emitting diodes (WLEDs). Selective occupation of Eu2+ in inorganic polyhedra with small coordination numbers results in broad-band red emission as a result of enhanced crystal-field splitting of 5d levels. Rb3YSi2O7:Eu exhibits a broad emission band at λmax=622 nm under 450 nm excitation, and structural analysis and DFT calculations support the concept that Eu2+ ions preferably occupy RbO6 and YO6 polyhedra and show the characteristic red emission band of Eu2+. The excellent thermal quenching resistance, high color-rendering index Ra (93), and low CCT (4013 K) of the WLEDs clearly demonstrate that site engineering of rare-earth phosphors is an effective strategy to target tailored optical performance.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liao H., Zhao M., Zhou Y., Molokeev M. S., Liu Q., Zhang Q., Xia Z.
Заглавие : Polyhedron Transformation toward Stable Narrow-Band Green Phosphors for Wide-Color-Gamut Liquid Crystal Display
Место публикации : Adv. Funct. Mater. - 2019. - Vol. 29, Is. 30. - Ст.1901988. - ISSN 1616301X (ISSN) , DOI 10.1002/adfm.201901988
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 91622125, and 51572023), 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).
Аннотация: A robust and stable narrow-band green emitter is recognized as a key enabler for wide-color-gamut liquid crystal display (LCD) backlights. Herein, an emerging rare earth silicate phosphor, RbNa(Li3SiO4)2:Eu2+ (RN:Eu2+) with exceptional optical properties and excellent thermal stability, is reported. The resulting RN:Eu2+ phosphor presents a narrow green emission band centered at 523 nm with a full width at half maximum of 41 nm and excellent thermal stability (102%@425 K of the integrated emission intensity at 300 K). RN:Eu2+ also shows a high quantum efficiency, an improved chemical stability, and a reduced Stokes shift owing to the modified local environment, in which [NaO8] cubes replace [LiO4] squares in RbLi(Li3SiO4)2:Eu2+ via polyhedron transformation. White light-emitting diode (wLED) devices with a wide color gamut (113% National Television System Committee (NTSC)) and high luminous efficacy (111.08 lm W−1) are obtained by combining RN:Eu2+ as the green emitter, K2SiF6:Mn4+ as the red emitter, and blue-emitting InGaN chips. Using these wLEDs as backlights, a prototype 20.5 in. LCD screen is fabricated, demonstrating the bright future of stable RN:Eu2+ for wide-color-gamut LCD backlight application.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Cheng C., Ning L., Ke X., Molokeev M. S., Wang Z., Zhou G., Chuang Y. -C., Xia Z.
Заглавие : Designing high-performance LED phosphors by controlling the phase stability via a heterovalent substitution strategy
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 2. - Ст.1901608. - ISSN 21951071 (ISSN), DOI 10.1002/adom.201901608
Примечания : Cited References: 31
Аннотация: Phosphor-converted white light-emitting diodes (LEDs) are currently playing key roles in the lighting and display industries and trigger urgent demands for the discovery of “good” phosphors with high quantum efficiency, improved thermal stability, and controllable excitation/emission properties. Herein, a general and efficient heterovalent substitution strategy is demonstrated in K2HfSi3O9:Eu2+ achieved by Ln3+ (Ln = Gd, Tb, Dy, Tm, Yb, and Lu) doping to optimize luminescence properties, and as an example, the Lu3+ substitution leads to improvement of emission intensity and thermal stability, as well as tunable emission color from blue to cyan. The structural stability and Eu2+ occupation via Lu3+ doping have been revealed by the structural elaboration and density functional theory calculations, respectively. It is shown that heterovalent substitution allows predictive control of site preference of luminescent centers and therefore provides a new method to optimize the solid-state phosphors for LEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lai S., Zhao M., Qiao J., Molokeev M. S., Xia Z.
Заглавие : Data-driven photoluminescence tuning in Eu2+-doped phosphors
Место публикации : J. Phys. Chem. Lett. - 2020. - Vol. 11, Is. 14. - P.5680-5685. - ISSN 19487185 (ISSN), DOI 10.1021/acs.jpclett.0c01471
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundations of China (Grant No. 51972118, 51961145101 and 51722202), Fundamental Research Funds for the Central Universities (D2190980), Guangzhou Science & Technology Project (202007020005), Guangdong Provincial Science & Technology Project (No. 2018A050506004), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). This work is also funded by RFBR according to the research project No. 19-52-80003
Предметные рубрики: Phosphors
Luminescence properties
Crystal structure
Ions
Quantum mechanics
Аннотация: Discovery of rare earth phosphors has generally relied on the chemical intuition and time-intensive trial-and-error synthesis; therefore, finding new materials assisted by data-driven computations is urgent. Herein, we utilize a regression model to predict the emission wavelengths of Eu2+-doped phosphors by revealing the relationships between the crystal structure and luminescence property. The emission wavelengths of [Rb(1–x)K(x)]3LuSi2O7:Eu2+ (0 ≤ x ≤ 1) phosphors, as examples for the data-driven photoluminescence tuning, are successfully predicted on the basis of the existing data of only eight systems, also consistent with the experimental results. These phosphors can be excited by blue light and exhibit broad-band red and near-infrared emission ranging from 619 to 737 nm. These findings in Eu2+-doped silicate phosphors indicate that data-driven computations through the regression mode would have bright application in discovering novel phosphors with a target emission wavelengths.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wei, Y.i., Yang, Hang, Gao, Zhiyu, Xing, Gongcheng, Molokeev M. S., Li, Guogang
Заглавие : Bismuth activated full spectral double perovskite luminescence materials by excitation and valence control for future intelligent LED lighting
Место публикации : Chem. Commun. - 2020. - Vol. 56, Is. 64. - P.9170-9173. - ISSN 1359-7345, DOI 10.1039/d0cc03975f. - ISSN 1364-548X(eISSN)
Примечания : Cited References: 27. - This work was supported by the National Natural Science Foundation of China (Grant No. 51672259) and the Fundamental Research Funds for the National Universities, China University of Geosciences (Wuhan) (No. 1910491T02)
Предметные рубрики: PHOTOLUMINESCENCE
PHOSPHORS
Bi3+
MODULATION
CRYSTAL
Аннотация: A novel La2Mg1.14Zr0.86O6:Bi3+ double perovskite phosphor with excitation-induced blue/green photoluminescence tuning is reported. By designing Bi3+ → Eu3+ energy transfer, single-composition white light with wide-scale adjustable corrected color temperatures (CCTs) is successfully achieved. This work initiates a new insight to explore phosphors with excitation-induced photoluminescence tuning and wide CCT control for future intelligent LED lighting.
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11.

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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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lim, Chang Sung, Atuchin V. V., Aleksandrovsky A. S., Denisenko, Yuriy G., Molokeev M. S., Oreshonkov A. S.
Заглавие : Fabrication of Microcrystalline NaPbLa(WO4)3:Yb3+/Ho3+ Phosphors and Their Upconversion Photoluminescent Characteristics
Место публикации : Kor. J. Mater. Res. - 2019. - Vol. 29, Is. 12. - P.741-746. - ISSN 1225-0562, DOI 10.3740/MRSK.2019.29.12.741. - ISSN 2287-7258 (eISSN)
Примечания : Cited References: 28. - This study was supported by the Research Program through the Campus Research Foundation funded by Hanseo University in 2019 (191Yunghap09) and the Russian Science Foundation (19-42-02003). The authors are grateful for the support from RFBR, according to the research project 18-32-20011.
Аннотация: New triple tungstate phosphors NaPbLa(WO4)3:Yb3+/Ho3+ (x = Yb3+/Ho3+ = 7, 8, 9, 10) are successfully fabricated by microwave assisted sol-gel synthesis and their structural and frequency upconversion (UC) characteristics are investigated. The compounds crystallized in the tetragonal space group I41/a and the NaPbLa(WO4)3 host have unit cell parameters a = 5.3927(1) and c = 11.7961(3) Å, V = 343.05(2) Å3, Z = 4. Under excitation at 980 nm, the phosphors have yellowish green emissions, which are derived from the intense 5S2/ 5F4 → 5I8 transitions of Ho3+ ions in the green spectral range and strong 5F5 → 5I8 transitions in the red spectral range. The optimal Yb3+:Ho3+ ratio is revealed to be x = 9, which is attributed to the quenching effect of Ho3+ ions, as indicated by the composition dependence. The UC characteristics are evaluated in detail under consideration of the pump power dependence and Commission Internationale de L'Eclairage chromaticity. The spectroscopic features of Raman spectra are discussed in terms of the superposition of Ho3+ luminescence and vibrational lines. The possibility of controlling the spectral distribution of UC luminescence by the chemical content of tungstate hosts is demonstrated.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ming, Zhiqiang, Qiao, Jianwei, Molokeev M. S., Zhao, Jing, Swart, Hendrik C., Xia, Zhiguo
Заглавие : Multiple substitution strategies toward tunable luminescence in Lu2MgAl4SiO12:Eu2+ phosphors
Место публикации : Inorg. Chem. - 2020. - Vol. 59, Is. 2. - P.1405-1413. - ISSN 0020-1669, DOI 10.1021/acs.inorgchem.9b03142. - ISSN 1520-510X (eISSN)
Примечания : Cited References: 31. - This research is supported by the National Natural Science Foundation of China (Grants 51972118, 51722202, and 51572023), Natural Science Foundations of Beijing (Grant 2172036), and Fundamental Research Funds for the Central Universities (Grant FRF-TP-18-002C1)
Предметные рубрики: Physical and chemical processes
Phosphors
Luminescence
Cations
Ions
Аннотация: The equivalent or heterovalent substitution strategy is an efficient way to stimulate photoluminescence tuning or to optimize the luminescence performances of phosphor materials. Garnet-type compounds receive much attention as phosphor hosts because of their flexible structural frameworks. Herein, a garnet-type Lu2MgAl4SiO12:Eu2+ phosphor with broad-band blue-green emission is first explored with two-site occupation by varying the Eu2+ content. Two host-substitution approaches to controlling the luminescence behavior of Lu2MgAl4SiO12:Eu2+ phosphor are implemented. The cation substitution strategy of Ca2+ for Mg2+ achieves tunable emission from 463 to 503 nm together with broadening emission bands in Lu2Mg1–yCayAl4SiO12:Eu2+ phosphors. Moreover, chemical unit cosubstitution of [Ca2+–Ge4+] replacing [Lu3+–Al3+] results in Lu2–zCazMgAl4–zGezSiO12:Eu2+ phosphors, which induce a red shift of the emission peak of about 60 nm and a broadening in the emission spectra with increasing Ca2+ and Ge4+ concentrations. The possible photoluminescence tuning mechanism is ascribed to the coordination sphere variation in the EuO8 polyhedron depending on the changing neighboring cations. The proposed approaches on equivalent or heterovalent substitution can contribute to the development of Eu2+-activated garnet-type phosphors with regulation of the luminescence performance and further initiate research discovering new phosphors for white-light-emitting diodes.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang, Ningzi, Molokeev M. S., Liu, Quanlin, Xia, Zhiguo
Заглавие : Pure red upconversion luminescence and optical thermometry of Er3+ doped sensitizer-rich SrYbInO4 phosphors
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 27. - P.7361-7366. - ISSN 2050-7526, DOI 10.1039/c8tc02565g. - ISSN 2050-7534(eISSN)
Примечания : Cited References:34. - The present work was supported by the National Natural Science Foundation of China (Grant 91622125, 51722202 and 51572023) and the Natural Science Foundations of Beijing (2172036), and M. Molokeev acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Предметные рубрики: TEMPERATURE-SENSING BEHAVIOR
EMISSION
NANOCRYSTALS
LANTHANIDE
Аннотация: Er3+ doped sensitizer-rich SrYbInO4 upconversion phosphors with an orthorhombic structure (Pnma) were synthesized by using a high temperature solid state reaction and their phase structure, site occupation and microstructure have been analyzed. Interestingly, upon the excitation from 980 nm pulsed laser diodes, the SrYbInO4:Er3+ phosphor emitted a nearly pure red emission on account of the 4F9/2 → 4I15/2 transition of Er3+. Additionally, based on the pump power dependence of the upconversion intensity and the schematic diagram of the energy levels, the upconversion mechanism in this system was verified in a two-photon process. The temperature-dependent behaviors of the as-synthesized sample demonstrated the potential for applications in optical thermometry.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou, Guojun, Jiang, Xingxing, Zhao, Jing, Molokeev M. S., Lin, Zheshuai, Liu, Quanlin, Xia, Zhiguo
Заглавие : Two-dimensional-layered perovskite ALaTa2O7:Bi3+ (A = K and Na) phosphors with versatile structures and tunable photoluminescence
Место публикации : ACS Appl. Mater. Interfaces. - 2018. - Vol. 10, Is. 29. - P.24648-24655. - ISSN 1944-8244, DOI 10.1021/acsami.8b08129
Примечания : Cited References: 48. - The authors acknowledge the support from the National Natural Science Foundation of China (Nos. 51722202, 91622125, and 51572023) and the Natural Science Foundations of Beijing (2172036) and RFBR (17-52-53031).
Предметные рубрики: GENERALIZED GRADIENT APPROXIMATION
YELLOW-EMITTING PHOSPHOR
Ключевые слова (''Своб.индексиров.''): 2d-layered perovskite--bi3+ emission--ion exchange--photoluminescence tuning--white light leds
Аннотация: Topological chemical reaction methods are indispensable for fabricating new materials or optimizing their functional properties, which is particularly important for two-dimensional (2D)-layered compounds with versatile structures. Herein, we demonstrate a low-temperature (∼350 °C) ion exchange approach to prefabricate metastable phosphors ALa1–xTa2O7:xBi3+ (A = K and Na) with RbLa1–xTa2O7:xBi3+ serving as precursors. The as-prepared ALa0.98Ta2O7:0.02 Bi3+ (A = Rb, K, and Na) share the same Dion–Jacobson type 2D-layered perovskite phase, and photoluminescence analyses show that ALa0.98Ta2O7:0.02 Bi3+ (A = Rb, K, and Na) phosphors exhibit broad emission bands peaking at 540, 550, and 510 nm, respectively, which are attributed to the nonradiative transition of Bi3+ from excited state 3P1 or 3P0 to ground state 1S0. The various Bi3+ local environments at the crystallographic sites enable the different distributions of emission and excitation spectra, and the photoluminescence tuning of ALa0.98Ta2O7:0.02 Bi3+ (A = Rb, K, and Na) phosphors are realized through alkali metal ion exchange. Notably, the combination of superior trivalent bismuth emission and low-temperature ion exchange synthesis leads to a novel yellow-emitting K(La0.98Bi0.02)Ta2O7 phosphor which is successfully applied in a white LED device based on a commercially available 365 nm LED chip. Our realizable cases of this low-temperature ion exchange strategy could promote exploration into metastable phosphors with intriguing properties.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Qiao, Jianwei, Ning, Lixin, Molokeev M. S., Chuang, Yu-Chun, Liu, Quanlin, Xia, Zhiguo
Заглавие : Eu2+ site preferences in the mixed cation K2BaCa(PO4)2 and thermally stable luminescence
Место публикации : J. Am. Chem. Soc. - 2018. - Vol. 140, Is. 30. - P.9730-9736. - ISSN 0002-7863, DOI 10.1021/jacs.8b06021
Примечания : Cited References: 40. - This work is supported by the National Natural Science Foundation of China (No. 51722202, 91622125, 51572023, and 11574003), Natural Science Foundations of Beijing (2172036) and M.M. acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Предметные рубрики: LIGHT-EMITTING-DIODES
SOLID-SOLUTION
PHOSPHORS
GREEN
BLUE
Аннотация: Site preferences of dopant Eu2+ on the locations of K+, Ba2+, and Ca2+ in the mixed cation phosphate K2BaCa(PO4)2 (KBCP) are quantitatively analyzed via a combined experimental and theoretical method to develop a blue-emitting phosphor with thermally stable luminescence. Eu2+ ions are located at K2 (M2) and K3 (M3) sites of KBCP, with the latter occupation relatively more stable than the former, corresponding to emissions at 438 and 465 nm, respectively. KBCP:Eu2+ phosphor exhibits highly thermal stable luminescence even up to 200 °C, which is interpreted as due to a balance between thermal ionization and recombination of Eu2+ 5d excited-state centers with the involvement of electrons trapped at crystal defect levels. Our results can initiate more exploration of activator site engineering in phosphors and therefore allow predictive control of photoluminescence tuning and thermally stable luminescence for emerging applications in white LEDs.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Jiang C., Brik M. G., Li L., Li L., Peng J., Wu J., Molokeev M. S., Wong K. -L., Peng M.
Заглавие : The electronic and optical properties of a narrow-band red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 12. - P.3016-3025. - ISSN 20507534 (ISSN), DOI 10.1039/c7tc05098d
Примечания : Cited References: 55. - We acknowledge the financial support received from the Program for Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_17R38), the Key Program of Guangzhou Scientific Research Special Project (Grant No. 201607020009), the National Natural Science Foundation of China (Grant No. 51672085, 51322208, 3160440), and the Fundamental Research Funds for the Central Universities. M. G. Brik acknowledges the supports received from the Recruitment Program of High-end Foreign Experts (Grant No. GDW20145200225), the Programme for the Foreign Experts offered by Chongqing University of Posts and Telecommunications, Ministry of Education and Research of Estonia, (Project PUT430) and European Regional Development Fund (Project TK141), and the Guest Professorship at Kyoto University (Prof. S. Tanabe laboratory). The first-principles calculations were carried out using the resources provided by the Wroclaw centre for Networking and Supercomputing (http://wcss.pl; Grant No. WCSS#10117290).
Ключевые слова (''Своб.индексиров.''): energy efficiency--gallium compounds--light emission--light emitting diodes--manganese--manganese compounds--optical properties--phosphors--precipitation (chemical)--quenching--rietveld refinement--sodium compounds
Аннотация: Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150-250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fm3m with the cell parameter a = 8.25320(4) Å. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti-Hirayama model, suggesting that the dipole-dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the red component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the red phosphor used in warm WLEDs.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zheng Y., Zhang H., Zhang H., Xia Z., Liu Y., Molokeev M. S., Lei B.
Заглавие : Co-substitution in Ca1−xYxAl12−xMgxO19 phosphors: local structure evolution, photoluminescence tuning and application for plant growth LEDs
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4217-4224. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00165k
Примечания : Cited References: 47. - The present work was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, and the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), and the Guangzhou Science & Technology Projects (No. 201704030086, 201605030005), and the reported study was funded by the RFBR according to the research project 17-52-53031. Special Funds for the Cultivation of Guangdong College Students’ Scientific and Technological Innovation (‘‘Climbing Program’’ Special Funds) were granted for Dr Yinjian Zheng.
Ключевые слова (''Своб.индексиров.''): co substitution--crystal structure transformation--high temperature solid-state reaction--lighting systems--local structure--luminescence measurements--structural refinement--tunable luminescences
Аннотация: Herein, Mn4+-activated Ca1-xYxAl12-xMgxO19 (x = 0-0.50) solid solutions were prepared using a conventional high-temperature solid-state reaction. Crystal structure transformation via chemical co-substitution of Y3+/Mg2+ for Ca2+/Al3+ was investigated in detail. The optical properties of Ca1-xYxAl12-xMgxO19 (x = 0-0.50) have been reported for the first time using a combination of techniques including structural refinement and luminescence measurements. Co-doping of Mg and Y cations within the CaAl12O19 host in a controlled manner resulted in the as-prepared samples with red/far-red ratio-tunable luminescence properties. The emission bands well-matched with the absorption band of phytochrome. Interestingly, enhanced Mn4+ luminescence can be obtained upon the addition of Mg2+ and Y3+. Unexpectedly, the quantum yields exhibit a slight change when x is in the range from 0.05 to 0.40; this indicates that these solid solutions have significant potential as lighting systems for plant growth.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liang S. S., Dang P. P., Li G. G., Molokeev M. S., Wei Y., Lian H. Z., Shang M. M., Al Kheraiff A. A., Lin J.
Заглавие : Controllable two-dimensional luminescence tuning in Eu2+,Mn2+ doped (Ca,Sr)9Sc(PO4)7 based on crystal field regulation and energy transfer
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 25. - P.6714-6725. - ISSN 2050-7526, DOI 10.1039/c8tc01825a. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 63. - This work was financially supported by the National Natural Science Foundation of China (NSFC No. 51672265, 51672266, 21521092, 51750110511, 51672257, and 51672259), the Key Research Program of Frontier Sciences of CAS (Grant No. YZDY-SSW-JSC018), the National Basic Research Program of China (2014CB643803), the Scientific and Technological Department of Jilin Province (Grant No. 20150520029JH and 20170414003GH), Jiangmen Innovative Research Team Program (2017) and Major Program of Basic Research and Applied Research of Guangdong Province (2017KZDXM083), the Russian Science Foundation (Grant No. 17-12-01047), and the Distinguished Scientist Fellowship Program of King Saud University, as well as the Deanship of Scientific Research at King Saud University through research group no. (RG-1939-038).
Предметные рубрики: SOLID-SOLUTION PHOSPHORS
LIGHT-EMITTING-DIODES
CATION SUBSTITUTION
Аннотация: Currently, controllable luminescence tuning and the generation of single component white emission are viable strategies to modify and optimize the luminescence performances of phosphors, which offer appealing prospects for the w-LED lighting industry. In this paper, we designed two-dimensional (2D) tunable color coordinates on the CIE diagram in the Eu2+,Mn2+ doped (Ca,Sr)9xSc(PO4)7 system by a combination of crystal field regulation and the energy transfer method. X-ray powder diffraction (XRD) and Rietveld refinement were utilized to analyze the phase composition and structural variation of the studied phosphors. The transmission electron microscopy (TEM) and photoluminescence spectra were exploited to analyze the generation of nanosegregation. The effects of the schedule of cation substitutions and energy transfer on the photoluminescence properties were investigated in detail. The corresponding luminescence mechanisms of the red-shifted emission with Sr2+ → Ca2+ substitution and Eu2+ → Mn2+ energy transfer were deeply discussed and proposed. In addition, the temperature-dependent thermal quenching behavior and the electroluminescence (EL) performance of the fabricated w-LED devices were also investigated to characterize the prepared Ca9(1−0.03−x−y)Sr9xSc(PO4)7:0.27Eu2+,9yMn2+. Finally, a representative w-LED device composed of a 369 nm UV chip and Ca9(1−0.03−0.02−0.5)Sr4.5Sc(PO4)7:0.27Eu2+,0.18Mn2+ could present excellent EL performance with the parameters CRI = 88, CCT = 3122 K and color coordinate (0.45, 0.44), which could well meet the commercial standard of warm white light. Therefore, our results suggest that this two-step luminescence tuning method is feasible to be applied in other phosphor systems for obtaining efficient white emitting phosphors.
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20.

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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