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438 results on '"Liu, Yan-gai"'

102. Tunable photoluminescence of apatite phosphor Ca5.95−xSrxLa4(SiO4)2(PO4)4O2:0.05Eu2+ and its application in light‐emitting diodes.

Author

Yu, Haojun, Xia, Yufei, Liu, Yan‐gai, Wang, Baochen, Huang, Zhaohui, and Fang, Minghao

Subjects
LIGHT emitting diodes, LED lamps, PHOSPHORS, APATITE, PHOTOLUMINESCENCE, EXCITATION spectrum
Abstract

A series of new apatite phosphors Ca5.95−xSrxLa4(SiO4)2(PO4)4O2:0.05Eu2+ (x = 0‐5.95) were prepared with the solid‐state method. The variations of the occupation rate and cell parameters were investigated in detail, demonstrating that the phosphors are pure phases and that the different occupation rates of La3+, Ca2+, and Sr2+ ions are due to the different electrostatic bond strengths. The reflectance and photoluminescence excitation spectra prove that the phosphors can be efficiently excited with near‐ultraviolet (n‐UV) light. The broad redshift (50 nm) in the photoluminescence spectra is attributed to the increase in the crystal field splitting when the Ca2+ ion is replaced by the larger Sr2+ ion. At 150°C, the obtained phosphors maintain an emission intensity of ~67%‐77% of that at room temperature (25°C), which indicates relatively the high performance of apatite phosphors in the temperature‐dependence experiment. Because of the substitution of the small Ca2+ ion by the large Sr2+ ion, the emission color changes from green to yellow. Finally, a series of self‐made light emitting diodes lamps were fabricated by coating the Ca5.95−xSrxLa4(SiO4)2(PO4)4O2:0.05Eu2+ phosphors with commercial blue and red phosphors on an n‐UV chip (λex = 370 nm). The self‐made white‐emitting lamps display a continuous changing correlated color temperature (4053‐9353 K) or commission international de L'eclairgae (from [0.29, 0.28] to [0.38, 0.37]), implying that the series apatite phosphors have great potential to meet the different requirements of applications. [ABSTRACT FROM AUTHOR]

Published
2019
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103. Research on slag‐resistance of ZrN‐SiAlON‐SiC‐C composite refractory in different atmospheres.

Author

Cheng, Bohao, Zhang, Zhijie, Wu, Xiaowen, Min, Xin, Huang, Zhaohui, Tao, Tianyi, Zhao, Haiqing, Fang, Minghao, and Liu, Yan‐gai

Subjects
COMPOSITE materials, SILICON carbide, SINTERING, OXIDATION, BLAST furnaces
Abstract

The ZrN‐SiAlON composite powder was synthesized using low‐grade zircon and bauxite by carbothermal reduction nitridation at first and then ZrN‐SiAlON‐SiC‐C composite refractory were fabricated with the ZrN‐SiAlON powder, SiC particles, and a small amount of Si powder as raw materials and sucrose as the binder. The slag resistance of these composites in O2, N2 and Ar atmosphere was investigated by X‐ray diffraction, scanning electron microscopy, and energy dispersion spectra. The results show that the pores in the inside of ZrN‐SiAlON‐SiC‐C composite refractory were enlarged in oxygen atmosphere due to oxidation, which leads to the decrease in slag resistance. In argon atmosphere, blast furnace slag destroyed the sintered body of zircon, corundum, and cristobalite with the formation of CaZrO3, then infiltrated into and filled the pores inside the refractory to form a dense layer, which hindered the further erosion of the blast furnace slag. In the reducing atmosphere, the interfacial energy of the gas‐liquid phases became larger due to the reactions between blast furnace slag liquid and the gas, resulting in a larger wetting angle which prevented the erosion. [ABSTRACT FROM AUTHOR]

Published
2019
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123. Crystal structure and luminescence properties of a single-component white-light-emitting phosphor Ca8ZnLa(PO4)7: Eu2+, Mn2+.

Author

Mi, Ruiyu, Liu, Yan‐gai, Mei, Lefu, Zhao, Chenglong, Chen, Jian, Huang, Zhaohui, and Fang, Minghao

Subjects
*CRYSTAL structure, *EMISSION control, *X-ray powder diffraction, *PHOSPHORS, *TRANSMISSION electron microscopy
Abstract

A series of novel green emission Whitlockite-type Ca8ZnLa(PO4)7:Eu2+ and color tunable Ca8ZnLa(PO4)7:Eu2+,Mn2+ phosphors were prepared by the solid-state reaction method in a reducing atmosphere. Its crystal structure and phase composition were identified by high-resolution transmission electron microscopy, selected area electronic diffraction, X-ray photoelectron spectroscopy, and X-ray powder diffraction Rietveld refinement, and it was found to be trigonal, belonging to R-3 c(161) space group. The luminescence properties of Eu2+ singly doped and Eu2+/Mn2+ codoped Ca8ZnLa(PO4)7 phosphors were revealed in detail. Ca8ZnLa(PO4)7:Eu2+ is excitable over a broad range from 200 to 450 nm with a prominent green emitting. With varied Eu2+/Mn2+ ratios, fine-tune emission under 365 nm excitation can be achieved from green (0.221, 0.468) to magenta (0.391, 0.276), especially the warm white light (0.392, 0.352), and CCT 3500 K can be obtained by the process of energy transfer between Eu2+ and Mn2+. The ET mechanism in this system is managed via the dipole-dipole interaction with the maximum energy-transfer efficiency 82.8% based on the decay lifetime data. These results suggest that as-prepared phosphors can serve as promising candidates of UV-pumped w- LEDs. [ABSTRACT FROM AUTHOR]

Published
2017
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124. Crystal structure and luminescence properties of a single-component white-light-emitting phosphor Ca8ZnLa(PO4)7: Eu2+, Mn2+.

Author

Mi, Ruiyu, Liu, Yan‐gai, Mei, Lefu, Zhao, Chenglong, Chen, Jian, Huang, Zhaohui, and Fang, Minghao

Subjects
CRYSTAL structure, EMISSION control, X-ray powder diffraction, PHOSPHORS, TRANSMISSION electron microscopy
Abstract

A series of novel green emission Whitlockite-type Ca8ZnLa(PO4)7:Eu2+ and color tunable Ca8ZnLa(PO4)7:Eu2+,Mn2+ phosphors were prepared by the solid-state reaction method in a reducing atmosphere. Its crystal structure and phase composition were identified by high-resolution transmission electron microscopy, selected area electronic diffraction, X-ray photoelectron spectroscopy, and X-ray powder diffraction Rietveld refinement, and it was found to be trigonal, belonging to R-3 c(161) space group. The luminescence properties of Eu2+ singly doped and Eu2+/Mn2+ codoped Ca8ZnLa(PO4)7 phosphors were revealed in detail. Ca8ZnLa(PO4)7:Eu2+ is excitable over a broad range from 200 to 450 nm with a prominent green emitting. With varied Eu2+/Mn2+ ratios, fine-tune emission under 365 nm excitation can be achieved from green (0.221, 0.468) to magenta (0.391, 0.276), especially the warm white light (0.392, 0.352), and CCT 3500 K can be obtained by the process of energy transfer between Eu2+ and Mn2+. The ET mechanism in this system is managed via the dipole-dipole interaction with the maximum energy-transfer efficiency 82.8% based on the decay lifetime data. These results suggest that as-prepared phosphors can serve as promising candidates of UV-pumped w- LEDs. [ABSTRACT FROM AUTHOR]

Published
2017
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125. '114'-Type Nitrides LnAl(Si4− xAl x)N7O δ with Unusual [AlN6] Octahedral Coordination.

Author

Huang, Zhaohui, Fang, Minghao, Liu, Yan-gai, Huang, Saifang, Ouyang, Xin, Cao, Peng, Gao, Wei, Zujovic, Zoran, Söhnel, Tilo, Price, Jason R., Avdeev, Maxim, Que, Meidan, Suzuki, Furitsu, Kido, Tsuyoshi, and Kaji, Hironori

Subjects
NITRIDES, COORDINATION compounds, ALUMINUM nitride, X-ray diffraction, OCTAHEDRAL molecules
Abstract

Aluminum-nitrogen six-fold octahedral coordination, [AlN6], is unusual and has only been seen in the high-pressure rocksalt-type aluminum nitride or some complex compounds. Herein we report novel nitrides LnAl(Si4− xAlx)N7O δ (Ln=La, Sm), the first inorganic compounds with [AlN6] coordination prepared via non-high-pressure synthesis. Structure refinements of neutron powder diffraction and single-crystal X-ray diffraction data show that these compounds crystallize in the hexagonal Swedenborgite structure type with P63 mc symmetry where Ln and Al atoms locate in anticuboctahedral and octahedral interstitials, respectively, between the triangular and Kagomé layers of [SiN4] tetrahedra. Solid-state NMR data of high-purity La-114 powders confirm the unusual [AlN6] coordination. These compounds are the first examples of the '33-114' sub-type in the '114' family. The additional site for over-stoichiometric oxygen in the structure of 114-type compounds was also identified. [ABSTRACT FROM AUTHOR]

Published
2017
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