Properties Of Up-conversion Emission Of Rare Earth Doped Oxyfluoride Nano Glass Ceramics

Rare earth ions doped oxyfluoride upconversion luminescence material already own a wide application in optical communication, upconversion laser,3D display, and data storage, but also defects like high energy phonon, low efficiency of upconversion, inconvenience of production, chemical instability, and low mechanic performances. With the deep study of upconversion luminescence, there has been major development of rare earth ions doped oxyfluoride upconversion luminescence glass-ceramics in recent years. With the low phonon energy of fluoride glass’s physics properties, the good physical and chemical stability and high mechanical strength of oxide glass, precipitation can be achieved by controlled crystallization of fluoride crystal phase. Since the low phonon energy of fluoride crystal phase, the rare-earth ions concentrate in the fluoride crystal phase, which can greatly enhance the upconversion luminescence efficiency of rare-earth ions. As a result, the fluoride-oxide luminescent glasses are highly promising rare-earth doped luminescent materials.This thesis uses a new formula to produce oxyfluoride glass ceramics, with raw material like SiO2, BaF2, Bi2O3, AIF3, Sr(NO3)2and rare earth oxide Er2O3, Tm2O3, and HO2O3. Through analysis Differential Thermal Analysis,680℃is adopted as the heat treatment crystallization temperature; by absorption spectrum and upconversion fluorescence spectrum, the crystallization time is set to2-4hours; and oxyfluoride glass ceramics is produced through heat treatment after X-ray diffraction experiment.This thesis analyzed on the spectrum of samples with Judd-Ofelt theory, and obtained the intensity parameters Ω2、Ω4、Ω6. Analyzed and compared, the optimum doping concentration of the rare earth ion was concluded, with spectral parameters, like radioactive lifetimes of samples, transition probabilities, and fluorescence branching ratio etc. Comparing the J-O intensity parameters before and after the heat treatment,Ω2、Ω4decreased sharply, mostly Ω2, and Ω6increased a little. and with comparison with other upconversion luminescence glass, this sample is believed with a lowest Ω2value, which means this glass has the highest covalency, the lowest matching symmetricity as rare earth structure, more likely to be excited and with a high intensity of emission spectrum.A set of Yb3+, Er3+, Tm3+, Ho3+ions double, triple and quadruple doped oxyfluoride glass ceramics were prepared for the red blue, and green upconversion luminescence mechanism in980mm laser excitation, including the energy inter-transference among Yb3+Er3+、Tm3+、Ho3+, the cross relaxation among rare earth ions, and the influences of density of ions on optical upconversion intensity of the colors. As for double dope mode, Er3+causes highest upconversion of green light, weaker upconversion of red light and weakest upconversion of blue light; Ho3+causes highest of red light, weaker of green light, and weakest of blue; Tm3+causes highest of blue light, weaker of red, and almost no green light. As for multiple doping mode, with the cross relaxation of rare earth ions and the reverse energy transference with Yb3+, the luminescence intensity varies as:with increase of Er3+intensity, green light intensity increases first then decreases, and both red and green light intensity decrease; with increase of Ho3+, red light intensity increases first then decreases, green light intensity changes little, and blue light decreases sharply; with increase of Tm3+blue light intensity increases first then decreases, both red and blue light decrease. Therefore, with adjustment of rare earth ions intensity in Yb3+, Er3+, Tm3+, Ho3+quadruple mode, with dope intensity of Er2O3(0.5wt%), Ho2O3(0.3wt%), Tm2O3(0.1wt%), white light emission can be achieved.