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Preparation And Properties Of Rare Earth Doped Perovskite - Type Composite Oxide

Posted on:2016-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:L FengFull Text:PDF
GTID:2271330461987058Subject:Analytical Chemistry
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Rare earth ions have stable physical and chemical properties, abundant level structure and longer lifetime. Under proper near UV or blue light excitation, rare earth ions can be doped into appropriate host as the activator, to get excellent luminescence properties. Rare earth doped phosphors is an important class of function materials, and the rare earth doped oxides phosphors could be widely used in the field of illumination and displays. The optical properties of rare earth ions show strong depends on the composition and structure of matrix materials, because of their unique 4f configuration, 4f5 d configuration and the charge transfer band structure. Therefore, in the exploration of new phosphors, a selection of new host materials to enhance the optical properties is a major concern.Perovskite composite oxides since it has stable structure and excellent performance, caused people more and more interest in recent years. In addition, the crystal type of perovskite composite oxide contains very rich, and allows a large number of ion substitution, so the optical properties of rare earth-doped perovskite composite oxides show well research value and potential applications.In this thesis, we synthesized a series of rare-earth-doped-perovskite composite oxides through a simple hydrothermal synthesis, and explore the optimal synthesis conditions, study on the optical properties of the rare earth ions(mainly Eu3+) doped in different matrix materials. The main contents in this thesis are as follows:(1) Controlled synthesis and novel photoluminescence properties of BaTiO3:Eu3+/Eu2+ nanocrystals. Tetragonal phase BaTiO3:Eu nanocrystals were successfully synthesized using a hydrothermal method and a subsequent calcination treatment. The structures and morphologies of nanocrystals were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The photoluminescence properties of BaTiO3:Eu were investigated in detail. Under 398 nm excitation, the emissions from Eu2+ and Eu3+ ions were observed, indicating that Eu2+ and Eu3+ ions coexisted in BaTiO3:Eu nanocrystals. Especially, the emission band of Eu2+ from BaTiO3:Eu was observed to broaden with increasing Eu concentration. When the Eu concentration was 0.5 mol%, the 5D0â†'7F0 and 5D1â†'7F0 emissions were observed. In addition, under 537 nm excitation, the emission intensity increased with increasing Eu concentration.(2) Photoluminescence and photocatalytic activity of Bi2MoO6:Ln3+ Nanocrystals. Sheet-like Bi2MoO6:Ln3+ nanocrystals were synthesized by a hydrothermal method. The crystalline size of Bi2MoO6:Ln3+(Ln = Eu and Gd) nanocrystals changes with the increasing of Ln3+ content in the reaction solutions gradually. The photoluminescence properties of Bi2MoO6:Ln3+ nanocrystals were investigated in detail. In the emission spectra of Bi2MoO6:Eu3+ nanocrystals, the 5D0 â†' 7F2 is much stronger than the 5D0 â†' 7F1. When the excitation is performed at 467 nm, the emission intensity is the strongest. The relative intensity of the transitions from Eu3+ increases with increasing Eu3+ concentrations, up to about 50 mol%, and then decreased abruptly. In the excitation spectra of Bi2MoO6:Eu3+(30%)/Gd3+ monitored at 618 nm, the 7F0 â†' 5D2(?467 nm) transition is dominating when the Gd3+ concentrations were 10% or 20%. When the Gd3+ concentrations were 30%, the 7F0 â†' 5D1(?538 nm) transitions is dominating. In addition, the photocatalytic activity of Bi2MoO6:Eu3+ was evaluated by the degradation of rhodamine B(RhB) aqueous solution under simulated solar light. The best photocatalytic performance was observed when the Eu3+ concentration was 1%.
Keywords/Search Tags:rare earth ions, perovskites, nanocrystal, luminescence, hydrothermal method
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