Charge compensation plays a very important role in modifying the local atomic structure and moreover the spectroscopic property of an isolated luminescent center, and so has been widely adopted in phosphor designs. In...Charge compensation plays a very important role in modifying the local atomic structure and moreover the spectroscopic property of an isolated luminescent center, and so has been widely adopted in phosphor designs. In this work, we carry out first-principles calculations on various cases of Ce3＋ centers in Ca3Sc2Si3O12 by considering the effects of the charge com- pensations related to N3-, Sc3＋, Mn2＋, Mg2＋, and Na＋. Firstly, the local structures around Ce3＋ are optimized by using density functional theory calculations with supercell model. The 4f→5d transition energies of Ce3＋ are then obtained from the CASSCF/CASPT2/RASSI-SO calculations performed on Ce3＋-centered embedded clusters. The calculated energies support the previous assignments of the experimental spectra. Especially, a previously unclear peak is identified to be caused by Sc3＋ substituting Si4＋. The results show that the first-principles calculations can be used as an effective tool for predicting and interpreting spectroscopic properties of the phosphors.展开更多
We described the synthesis and luminescence of Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ phosphor for light emitting diode （LED）. The crystal-linity, morphology, structure, and luminescence spectra were examined by X-ray diffr...We described the synthesis and luminescence of Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ phosphor for light emitting diode （LED）. The crystal-linity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy. The results showed that Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ phase was a dominating phase with little impurity phase peaks of Y2O3 when the sintered temperature reached to 1400 oC. Field emission scanning electron microscopy （FE-SEM） images showed the particle size of the phosphor was about 3 μm. Meanwhile, the excitation and emission spectra indicated that the as-prepared phosphors could be effectively excited by blue （460 nm） light and the excitation spectrum showed a broad band extending from 400-500 nm, while emission spectrum showed a broad yellow band peaking at 534 nm. The decay curve at the emission peak consisted of fast and slow components. The Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ should be a promising yellow phosphor for near blue-based white-light-emitting diodes （LEDs）.展开更多
基金This work was supported by the National Key Basic Research Program of China （No.2013CB921800）, the National Natural Science Foundation of China （No.11374291, No.11311120047, No.11274299, No.11447197, and No.11204292）, the Fundamen- tal Research Funds for the Central Universities （No.WK20304200）, the Anhui Provincial Natural Science Foundation （No.1508085QA09）. The numerical calculations have been partially done on the super- computing system in the Supercomputing Center of University of Science and Technology of China.
文摘Charge compensation plays a very important role in modifying the local atomic structure and moreover the spectroscopic property of an isolated luminescent center, and so has been widely adopted in phosphor designs. In this work, we carry out first-principles calculations on various cases of Ce3＋ centers in Ca3Sc2Si3O12 by considering the effects of the charge com- pensations related to N3-, Sc3＋, Mn2＋, Mg2＋, and Na＋. Firstly, the local structures around Ce3＋ are optimized by using density functional theory calculations with supercell model. The 4f→5d transition energies of Ce3＋ are then obtained from the CASSCF/CASPT2/RASSI-SO calculations performed on Ce3＋-centered embedded clusters. The calculated energies support the previous assignments of the experimental spectra. Especially, a previously unclear peak is identified to be caused by Sc3＋ substituting Si4＋. The results show that the first-principles calculations can be used as an effective tool for predicting and interpreting spectroscopic properties of the phosphors.
基金Project supported by National Natural Science Foundation of China (51172165)Key Foundation of Zhejiang Province Natural Science Foundation(Z4110347)+2 种基金Zhejiang Province Key Technology Innovation Team (2009R50010)Wenzhou Municipal Science and Technology Bureau Key Program (G20090082)Huzhou Municipal Natural Science Foundation (2011YZ02)
文摘We described the synthesis and luminescence of Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ phosphor for light emitting diode （LED）. The crystal-linity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy. The results showed that Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ phase was a dominating phase with little impurity phase peaks of Y2O3 when the sintered temperature reached to 1400 oC. Field emission scanning electron microscopy （FE-SEM） images showed the particle size of the phosphor was about 3 μm. Meanwhile, the excitation and emission spectra indicated that the as-prepared phosphors could be effectively excited by blue （460 nm） light and the excitation spectrum showed a broad band extending from 400-500 nm, while emission spectrum showed a broad yellow band peaking at 534 nm. The decay curve at the emission peak consisted of fast and slow components. The Ca1.5Y1.5Al3.5Si1.5O12：Ce^3＋ should be a promising yellow phosphor for near blue-based white-light-emitting diodes （LEDs）.
