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Study On Synthesis And Luminescent Properties Of LaPO4:Eu3+ Nano-materials

Posted on:2011-08-27Degree:MasterType:Thesis
Country:ChinaCandidate:Q LiuFull Text:PDF
GTID:2131330332963743Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Due to the unique optical properties, lanthanide nanophosphors have important applications in high-resolution displays, solid lasers and biological analysis. Establishing well-controlled synthetic strategies to these materials, understanding their growth and luminescent mechanism, and the relationships of their structures, morphologies and optical behaviors are crucial to the production of nanophosphors with designated optical properties.In this article, the chemical precipitation and molten salt method were used to synthesis LaPO4:Eu3+. The morphology, phase and luminescent preperties of reaction products were investigated by XRD, DTA, FT-IR, TEM, SEM, HRTEM and UV-vis, the effect of reaction pH values, thermal treatment temperatures, thermal treatment time and doped concentration of Eu3+ ion on the luminescent preperties were investigated. The experimental results showed that the morphology of products was needle-like synthesized by La2O3, Eu2O3 and Na3PO4·12H2O at room temperature, which has hexagonal phase and transformed to monoclinic phase after calcination at 500℃; the morphology of products was coral-like which was aggreated by single crystal nano-wier synthesized by La(NO3)3, Eu2O3 and H3PO4 at room temperature, this coral-like product has monoclinic phase and did not occur crystalline phase transformation with the temperature. The pH value of reaction system has great effect on the morphology, the strong acidic environment (pH=2) of the mother liquor favors growth rates along one crystallographic plane and in the strong basic environment (pH=12) the product were particle with the size smaller than 100nm. Photoluminescence analysis shows that the product has great photoluminescence property, the excitation spectra of phosphors was shown the peaks of 391nm in the UV region, and emission spectra of phosphors was nearly at 586nm. Since the 5D0-7F1transition, which is a magnetic dipole transition, is by far the most intense, indicating a centro-symmetrical environment for Eu3+ ions. The optical properties of LaPO4:Eu3+ are dependent on their structures and morphologies. The peak location of the CT band blue-shifed in hexagonal structure and the monoclinic structure of LaPO4:Eu3+ has great optical properties. The Photoluminescence properties of phosphors are changeable with the production conditions, such as thermal reatment temperatures, thermal treatment time and concentration of Eu3+ ions. The concentration quenching is due to Eu3+ ions exchange interactions. The synthesis conditions have been confirmed by contrasting Photoluminescence intensity, in strong acidic environment, the thermal reatment temperature and time is about 1000℃and 2 hours, the concentration of Eu3+ is 6mol%, respectively.In the second part, LaPO4:Eu3+ phosphors were successfully synthesized by molten salt method. The high crystallinity with monoclinic structure can be obtained at low temperature, the ratio of length to width and size of the product decreased with the increase of the thermal treatment temperature and molten salt concentration. Photoluminescence analysis shows that the product has great photoluminescence property, the emission spectra of phosphors was nearly at 586nm, which is characterized by orange-red emission. The Photoluminescence intensity decreased as the temperature increase. Contrasting the Photoluminescence intensity, the synthesis conditions have been confirmed:the thermal reatment temperature and time is about 500℃and 3 hours, the quantity ratio of precursor to molten salt is 1:6, respectively.
Keywords/Search Tags:Chemical precipitation method, Molten salt method, LaPO4:Eu3+, Photoluminescence
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