The Synthesis Of Fine Rare Earth Phosphor By Solid-state Reaction At Ambient Temperature And The Study On Its Fluorescent Properties

Rare earth luminescent materials have been widely applied because rare earth ion has abundant energy level and transition characteristic of 4f. At present, rare earth luminescent materials can be prepared by solid-state reactions at high temperature or precipitation in solution. It's difficult to obtain materials with high quality and fine granularity so that the application is restricted. So nano technologies on preparing rare earth luminescent materials have been studied widely in recent years.In this paper, fine Y₂O₃, Y₂O₃:Eu³⁺ and BaMgAl10O17 were synthesized by solid-state reaction at ambient temperature. Surface diffusion method was applied to adulterate Eu of blue phosphor. BaMgAl10O17:Eu²⁺ was gained after deoxidized by activated carbon. The effect of surfactants on granularity and morphology of fine phosphor was studied in this thesis. Different Temperature Analysis and Thermogravimetric(DTA-TG) were used to determined the decomposing temperature. X-ray Diffraction(XRD), Scanning Electronic Microscope(SEM), Laser Anemometer and Fluorescence Spectrophotometer were used to analyze the phosphors.Such conclusions can be drawn from our study.Y2(C2O4)3 and Y2(CO3)3 as precursors were synthesized by solid state chemical reaction between Y(NO3)3.6H2O and C2H2O4.2H2O or (NH4)2CO3 at ambient temperature. Y₂O₃ was prepared by decomposing precursor. The results of XRD and SEM show that oxides prepared by two complexants are Y₂O₃. The morphology of particles is spherical. It has stronger reflection effect on UVA and UVB. Y2(C2O4)3 and Eu2(C2O4)3 as Precursors were synthesized by solid-state chemical reaction among Y(NO3)3.6H2O, Eu2O3 and C2H2O4.2H2O. The result of XRD shows that cubic structure Y₂O₃:Eu³⁺ phosphor was prepared by decomposing the precursor at 700℃. Its morphology is spherical and the granularity of particles is within 164nm～396nm. The maximum excitation spectra peak of fine Y₂O₃:Eu³⁺ phosphor is at 250nm corresponding to Eu³⁺ and O2- charge-transfer state transition. The maximum emission spectra peak is at 618nm corresponding to 5D0→7F2 transition. The luminescent intensity increase with the growth of Eu³⁺ concentration at the beginning, then intensity drops when Eu³⁺ concentration is beyond 8%. The optimal concentration of Eu³⁺is 8%. It is also found the luminescent intensity increases slowly with calcining temperature up to 1100℃.Blue phosphor was synthesized by solid-state chemical reaction and surface diffusion method. The result of XRD shows that BaMgAl10O17 was prepared by decomposing precursor at 1200℃. Its morphology is spherical and granularity of particles is within 342nm～531nm. Fine BaMgAl10O17:Eu²⁺ phosphor has broad emission band at 255nm and 330nm separately corresponding to 4f-5d transition of Eu²⁺. The maximum emission spectra peak is at 450nm corresponding to 4f65d→4f7(8S7/2)transition of Eu²⁺. The luminescent intensity increase with the growth ofEu²⁺ concentration at the beginning, then intensity drops when Eu²⁺concentration is beyond 10%. The optimal concentration of Eu²⁺is 10%.Surfactant was added in the reaction system during the synthesis process. The morphology, decentrality and granularity of phosphor were studied. The results indicate that phosphor synthesized by adding surfactant has finer particle more regular morphology and better decentrality than synthesized without surfactant. Above all, the surfactant is helpful to improve the dispersion and decrease the size of the products.