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Total Precipitation Synthesis Of Sr <sub> 2 </ Sub> Of Ceo <sub> 4 </ Sub> And Sr <sub> 2 </ Sub> Of Ceo <sub> 4 </ Sub>: Re (re = Eu, Of Sm, Er, Gd) Materials, Luminescent Properties

Posted on:2008-02-04Degree:MasterType:Thesis
Country:ChinaCandidate:J M LiFull Text:PDF
GTID:2191360215475808Subject:Physical chemistry
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With the rapid developments of new technology, luminescent materials science and technology have attracted much attention. Today, luminescent materials play important roles in many fields of the society, and the cognition and research work on them have capacious academic value and practical application. The accession of rare earth elements brings the remarkable improvement to the luminescent materials, being a bout of revolution relative to the traditional luminescent materials. Thus the rare earth luminescent materials become the research focus more and more.Sr2CeO4 is a new and efficient blue emission powder phosphor, It can also be regarded as the host material besides giving out light itself. Co-precipitation has been used to prepare the precursor of Sr2CeO4 via different precipitants. However the fluorescent performances of Sr2CeO4 synthesized by different precipitants were not compared.In this paper, we prepared Sr2CeO4 and Sr2CeO4: RE (RE= Eu, Sm, Er, Gd) by co-precipitation.Here, the synthesis of Sr2CeO4 powders through chemical co-precipitation using ammonium oxalate or ammonium carbonate as precipitants was reported. The optimum conditions to prepare Sr2CeO4 phosphor powder should use the carbonate precursor, and raise the heating temperature to 1250°C.Ce4+'Eu3+ energy transfer exists in Sr2CeO4: Eu3+. Under the excitation of UV light, with the increase of the Eu3+ concentration form low (1 mol%) to high (10 mol%), the emission light changes from blue-white to red-white. In addition, the energy transfer phenomenon of Gd3+'Eu3+ in Sr2CeO4: Eu3+,Gd3+ was observed. When the Gd3+ concentration is 3 mol%, the optimum Eu3+ luminescent effect in Sr2CeO4: Eu3+, Gd3+ is achieved.In the experiment of Sr2CeO4: Sm, we confirm the optimum heating temperature and the Sm3+ concentration. In spite of the sintering period only takes 3 h, the intensity of emission spectra is twice as that of which was synthesized by conventional high temperature solid state reaction and sintered for 30 h.All the time, Er3+ has been concerned abroad due to up-conversion emissions. Sr2CeO4: Er phosphor was prepared, and green up-conversion emissions (547 nm) and red up-conversion emissions (644 nm) was observed. When the Er3+ concentration is 2 mol%, the sample has the best effect of up-conversion emissions.The novel studies of the work are in the following:(1) We compared the fluorescent effect of Sr2CeO4 synthesized by different precipitants and confirmed the optimum condition of preparation.(2) Although the heat-treatment period was decreased greatly as compared with conventional solid state reaction, the luminescence efficiency was evidently improved. No doubt, they are suitable to the application of luminescent materials.
Keywords/Search Tags:Sr2CeO4, Sr2CeO4: RE, Luminescence, Energy transfer, Co-precipitation
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