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Study on the Up-conversion Luminescence Properties of Er3+，Yb3+ Doped Rare-earth Stannate Nanocrystals

Author: ChenJu
Tutor: ZhangWeiFeng
School: Henan University
Course: Condensed Matter Physics
Keywords: Ln2Sn2O7 Er3+nanocrystals pyrochlore structure Er3+/Yb3+ Up-conversion luminescence Sol-gel method SPS
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Type: Master's thesis
Year: 2013
Downloads: 148
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Abstract


Many excellent optical, electrical, magnetic, superconducting properties of rare earth compoundsexhibit have and rare earth ions on special4f electronic configuration and4f5d energy level structure,especially rare earth elements has spectral properties of general elements are incomparable, so rare earthluminescent materials has become the preferred materials in the field of information processing, stereodisplay, fluorescence marker, the present study of rare earth luminescent material is causing widespreadconcern and interest. The nanometer luminescent materials because of its special properties and is verylikely to become the new luminescent materials for the next generation. In many of the nanostructuredluminescent materials, the pyrochlore structure composite oxide as the host material has the most attractivefor rare earth doped material matrix. Because of the very good physical and chemical stability whichpyrochlore structure composite oxide has so it also has excellent luminescent properties, and now has beenwidely applied to information display, lighting engineering, optical communication and other realms.Multiple complex oxides of rare earth stannate belongs to the pyrochlore structure, which has excellentthermal, electrical, magnetic and catalytic properties, so they show great potential applications in ionconductor, fluorescence, lithium battery, catalyst and radiation field. Rare earth ions, especially Er3+ionswhich has rich radiation level, the long excited level service life, easy to be direct excitated by low photonenergy, conversion efficiency is very high and other advantages, they very suitable as up-conversionluminescence materials center. So, in order to find the excellent luminescent materials, we use rare earthstannate as matrix materials, the Er3+ion as fluorescent center. In this thesis, we use sol-gel methodcombining several stannate nanocrystal materials, and systematic study on the luminescence properties.The main content of this thesis and the conclusions obtained are as follows:1. We successfully prepared nanocrystal Er3+doped La2Sn2O7phosphors by the sol-gel method. Theresults show that: La2Sn2O7: Er3+nanocrystals are cubic pyrochlore structure, the crystal morphologysimilar as octahedral. We can observe that all these nanocrystals can give the green emission （517-575nm）and red emission （644-690nm）, which are attributed to the intra-4f transition of4H11/2,4S3/2→4I15/2and4F9/2→4I15/2of Er3+ions, respectively. The optimal doping concentration of Er3+is found to be7mol%, the optimal annealing temperature is1150℃.2. This chapter we prepared Gd2Sn2O7: Er3+nanocrystals by Sol-gel method with different annealingtemperature and different Er3+doping concentration. The up-conversion emission spectrum of the samplesare measured under the excitation of a980nm continuous wave diode laser under the room temperature,which can produce three strong upconversion emission peak around527,563,661nm. Analysis of theoptimal doping content and annealing temperatures of Er3+are found to be5mol%and1050℃.3. Er3+and Yb3+ions co-doped La2Sn2O7nanocrystals are synthesized by sol-gel method. Analysis ofthe influence of crystal structure of different substrates on the up-conversion emission intensity we find thatthe best luminescence is the La2Sn2O7as the substrate. The up-conversion luminescence intensity of Er3+ions is enhanced greatly by addition of various contents of Yb3+ions, and the optimal doping concentrationis3mol%of Yb3+ions.4. We prepared La2Sn2O7:Er3+//SnO2nanocrystals by sol-gel method. The structure and morphology ofthe samples which are characterized by XRD and SEM, the results show that the sample is a mixture ofLa2Sn2O7and SnO2. At the same time we compare and explain the excitation of a980nm continuous wavediode laser which at different temperature, we can see that the up-conversion luminescence intensity isdifferent, and the optimal annealing temperature is1100℃. We also explore the surface photovoltageproperties of the samples, the induced electric field can enhance its optical voltage value, but thephotovoltage spectrum broadening is not to visible region.

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