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First-principles Study On Strontium Aluminate Long Afterglow Luminescent Materials

Posted on:2017-05-25Degree:MasterType:Thesis
Country:ChinaCandidate:X WuFull Text:PDF
GTID:2271330482972399Subject:Materials Science and Engineering
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In recent years, strontium aluminate long afterglow luminescent materials have been widely used in various fields, despite a lot of the experimental study of SrAl2O4 the electronic structure and luminescence characteristics, but there are still differences in terms of reaction conditions and light emission mechanism. The research on agents and auxiliary activator is not under way deeply, to limit the practical application of strontium aluminate long afterglow luminescent material. This paper researches the synthesis conditions, electronic structure and luminescence of SrAl2O4 by high temperature solid-phase method and the first-principles method.This paper dealed the reaction temperature, reaction time and the ratio of the doping Dy2O3, Eu2O3 and luminescent properties of the product, which raw materials of SrCO3, Al2O3, Eu2O3 and Dy2O3 was fully reacted by the high temperature solid phase method in a vacuum sintering furnace. The results showed that: the best synthetic condition of SrAl2O4:Eu2+,Dy3+ is reaction temperature 1500℃ and reaction time 3h; when Eu2O3 doping amount is 2wt%, SrAl2O4:Eu2+ luminous intensity is the largest, afterglow performance is best; when Eu2O3 doping amount of 2wt%, Dy2O3 doping quantity is 4wt%, SrAl2O4:Eu2+,Dy3+ the luminous intensity is the largest, afterglow performance is best.The SrAl2O4, SrAl2O4:Eu2+, SrAl2O4:Eu2+,Dy3+ electronic structure and the role of Eu and Dy in SrAl2O4 crystals investigated by first principles method respectively. The results show that SrAl2O4 crystal cell volume decreases after the Eu’s doping. The cohesive strength between O and Al is greater than the binding force between O and Sr. Eu doping makes covalent enhancement between the Sr and O, Al and O. SrAl2O4 is indirect semiconductor, valence band is mainly contribution by the O 2p orbit, conduction band is mainly contribution by the Sr 4d orbit. After blending Eu, Fermi level up, in the forbidden band Eu 4f orbit, appeared in the conduction band Eu 5d orbit, under the condition of illumination, Eu 4f orbit of electron in the band gaps are 5d to the conduction band of the Eu’s orbit, after the light, the electron jump from the excited state back to the ground state, in the form of light energy out, issued a yellow green with 519 nm. Eu and Dy doping, in Eu 4f orbit and Eu 5d orbit neighborhood there is Dy 4f orbit and Dy 5d orbit, when the light irradiate, the electron transition hole to be captured in Dy trap energy level, when the light stop, Dy trap energy level capture hole slow release, and in combination with the electronic which transition back to the ground state, release energy in the form of light. So the SrAl2O4:Eu2+,Dy3+ has a good long afterglow luminescence performance.
Keywords/Search Tags:Long afterglow luminescent materials, SrAl2O4, Frist principle, Band structures, Density of states
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