High-purity Fluorescent Material Y <sub> 2 </ Sub> O <sub> 2 </ Sub> S Preparation Of Ti Doped Optical Properties Study

In the rencent years, the luminescence material study is an important subject of the condensed matter physics due to its broad applications and complex physical phenomena. Among them, the research on Y₂O₂S and its doped phosphor is one of the most important topics.It is difficult to prepare the pure Y₂O₂S due to the enormous difference of melt point between S and Y2O3. In this thesis, the preparation technology has been described and the Y₂O₂S was prepared by a new high temperature solid-vapor reaction method between solid-state Y2O3 and vapour S. XRD pattern indicate that the product has ideal phase structure, no second phase or impurity peaks were observed. The purity of phosphor has been improved due to no solvent was used. The luminescence of Ti droped Y₂O₂S enhance about 23 times than that of traditional production, which was produced by the solvent method. The visible Raman spectrum is in accord with the pioneer report very wall.To the best of our knowledge, the research of the optics and other physical characteristic of Y₂O₂S was only done by a few of research group, and no report discuss the temperature dependence of Y₂O₂S Raman spectra so far, because of the difficult on the fabrication of pure Y₂O₂S,. In our work, the Raman scatter research shows that the temperature dependence of the Raman shift and FWHM of Y₂O₂S can be described by a non-linearity function approximately. The various vibration modes show different temperature dependence, which could originate from the anisotropic of Y₂O₂S crystal lattice.Since the fluorescence and long afterglow behavior of Ti doped oxide have been found, there are some reports discussed the luminescence characteristics of the Ti doped KTiOPO4, Al2O3, ZnO , NaCl and Y₂O₂S etc, and some physical models have been proposed to explain the observed experiment phenomenon. However there are a number of physical problems are still open. In this work, we studied the luminescence behavior and electron structure of Ti0.09Y1.91O3 and Ti0.09Y1.91O2S systematically. Our experiment study shows that the cubic Ti0.09Y1.91O3 changes into trigonal Ti0.09Y1.91O2S due to the replacement of S for O, and the energy band structure and photoluminescence spectrum were also changed. XPS study reveals that the Ti is in quadrivalence state, no Ti2+ and Ti3+ ions were found in Ti0.09Y1.91O3 and Ti0.09Y1.91O2S. The relative shift of core level Ti-2p and valence band between the two compounds were observed. The electron structure variation leads to the shift of the emission spectrum of Ti0.09Y1.91O3 and Ti0.09Y1.91O2S. At the same time, the up-conversion spectrum of Ti0.09Y1.91O2S was observed at about 383 nm, which was attributed to two photons effect, but the up-conversion spectrum of Ti0.09Y1.91O3 is not observed. A simple model has been proposed to discuss the experimental phenomenon.