Study On Order-Disorder Transition Of Zeolites And Prepration Of Upconversion Luminescence Material

Although silica (SiO2), amorphous or crystal, has excellent mechanical, optical, electrical, and thermal properties, and a wide variety of technological applications, there are still some drawbacks and limitations from itself. A traditional method to prepare bulk silica glass is the melt-quenching technique which requires very high temperatures in excess of～2000℃. The high phonon energy make it difficult to be upconversion luminescence matrix material. The order-disorder of ZSM-5provide a new approach to prepare silica material.Based on the amorphization of zeolites ZSM-5, an order-disorder transition method was used to prepare silica glass via Spark Plasma Sintering(SPS). The intermediate products, which can reflect the whole order-disorder transition process, are obtained by stopping sintering at different time and cooling with furnace rapidly. The samples were examined by X-ray diffraction, High-energy synchrotron X-ray diffraction, small-angle X-ray scattering, infrared absorption spectra,29Si magic angle NMR spectra, simultaneous thermal analysis, scanning electron microscopy to explore structural changes during order-disorder transition. Three main transformation regions have been divided to describe the whole process of order-disorder transition. Structural change does not occur until1190℃and the original state of ZSM-5still exist in the temperature ranging from1190℃to1270℃. Dramatic change in terms of phase and structure happens at temperature interval of1270～1310℃in which the intermediate range structure formed in collapsed process may give rise to specific property and be meaningful to material design. It is clear that amorphization lead to change intertetrahedra Si-O-Si angle and increase of coordination number. This paper discussed the temperature of amorphization induced by SPS, lower than that of temperature-induced amorphization, which make it a cost-saving approach.ZSM-5doped with the Rare earth nitrates by milling method as a precursor powder was sintered by spark plasma sintering. Though this methods, Yb3+/Er3+co-doped, Tm3+/Yb3+codoped and Yb3+/Ho3+co-doped upconversion luminescence material of silicate matrix were synthesized for the first time. The samples were examined by X-ray diffraction analysis (XRD), absorption spectroscopy and upconversion fluorescence spectroscopy. Under the excitation of980nm pump light, is used to excite the co-doped sample, not only excitation light source can be used more efficiently, but also enhanced conversion efficiency through energy transfer between Yb3+ions and Er3+/Tm3+/Ho3+ions. Upconversion luminescence material of Yb3+、Er3+co-doped system and Yb3+、Ho3+co-doped system can generate red and green upconversion emission phenomena and red light intensity is much higher than the green light. However, Yb3+、Tm3+co-doped system have a poor light emission in visible light region with very slight blue light, instead, the light centered at790nm can be detected. Material of Yb3+、Er3+co-doped system have wide range of illuminating from0.4%Yb3+,0.04%Er3+to4%Yb3+,0.4%Er3+. In Yb3+、Ho3+co-doped system, the sample with4%Yb3+,0.4%Er3+get the most intense light emission. Upconversion luminescence material obtained by this method was characterized by simple preparation process, excellent mechanical strength and corrosion resistance, etc..