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Research On The Preparation And Properities Of The Y2O2S:Eu~(3+) Luminescent Materials Via Hydrothermal Method

Posted on:2008-11-19Degree:MasterType:Thesis
Country:ChinaCandidate:Z X XuFull Text:PDF
GTID:2121360212489064Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
In this thesis, the preparation, performance and research development of red long-afterglow phosphors were summarized. The crystal structure of yttrium oxysulfide and luminescent property of rare-earth ions were reviewed. Based on these investigations and our research results that we already have achieved, a new preparation process has been proposed to prepare the Y2O2S:Eu3+ phosphors for long lasting afterglow application.The precursor of Y4O(OH)9(NO3):Eu3+ nanorod, which was prepared viahydrothermal reaction route from the starting Y(NO3)3 and KOH reactant system, was used to prepare Y2O2S:Eu3+ phosphor via a post sulfurization process during which the precursor with adjustable shape and size was transformed to final Y2O2S:Eu3+ product. The products were characterized by XRD, SEM, and PL spectra. The influence of synthesis condition and different Eu3+ concentration on the crystalline, morphology and luminescence properties of Y2O2S:Eu3+ product was investigated. The obtained results provide experimental support for the further study of Y2O2S - based long afterglow phosphors.A series of Y4O(OH)9NO3:xEu (x=0.02~0.15) precursors was synthesized through hydrothermal reaction route. The effect of different Eu3+ concentration on the luminescence spectra of the precursor was investigated. It was found that the nano-structure and morphology of Y4O(OH)9(NO3) nanorod kept unchanged with the increase of Eu3+ doping level. The doped Eu3+ content could be as high as 15mol% in Y4O(OH)9NO3 precursor. The emission spectra of Y4O(OH)9NO3:xEu(x=0.02~0.15) precursors was composed of a series sharp emission lines which come from the 4f transition of Eu3+. The emission lines at 615 nm and 625 nm corresponding to the typical 4f transition result in the typical red luminescence. The relative intensity of main emission lines improved with increasing Eu3+ concentration, while the shape and position of emission peaks kept unchanged. The phenomenon of concentration saturation was not observed in the precursor when the concentration of Eu3+ was as high as 15mol%.The Y2O2S:Eu3+ product was prepared by sulfurizing the Y4O(OH)9NO3:Eu3+ precursor at N2 and CO atmosphere, respectively. The optimal synthesis condition was studied. It was found that Y2O2S:Eu3+ product could be obtained from precursor at N2 atmosphere only with the existence of flux which obviously reduced the sulfurization temperature. A single Y2O2S phase could be obtained at a relative low temperature of 600℃. The morphology of final Y2O2S:Eu3+ product prepared at different sulfurization temperatures differed significantly from each other. The grain was rod-like at 500℃ and 600℃ and it gradually transformed into hexagon at higher temperature.Under the CO atmosphere, a single Y2O2S phase was obtained at the sulfurization temperature of 1000℃ which is much higher than that in N2 atmosphere. For the emission spectra of the products, the main peaks at 615 nm and 625 nm were attributed to energy transition 5D0 to 7F2, both were characteristic of red-luminescence for the Y2O2S:Eu3+ phosphor. The relative intensity of main emission lines firstly improved with increasing sulfurzation temperature and time, then declined. So the suitable synthesis condition obtained in present study is sulfurization at 1200℃ for 2h. The grain was equally distributed with hexagon shape at such condition. Otherwise, the grain would grow distinctly or preferred orientation at higher sulfurization temperature or longer treatment time.A series of Y2O2S:Eu3+ products with different Eu3+ concentrations were prepared at CO atmosphere. The influence of Eu3+ concentration on the crystal structure and luminescence property was investigated. The results showed the doping of Eu3+ ions had little effect on the crystal structure and morphology of Y2O2S:Eu3+ product. The grains of all Y2O2S:Eu3+ products with different Eu3+ concentrations were hexagon shape. The size dispersed evenly and changed little. The suitable Eu3+ concentration was 10 mol%, and the intensity of emission spectra reduced greatly when the concentration was above 14mol%.
Keywords/Search Tags:Y2O2S:Eu3+, hydrothermal process, red luminescence, long-afterglow, rare-earths
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