The Synthesis and Luminescence Investigation of Some New Phosphors for Vacuum Ultraviolet Excitation
| Autor: | Yi-Rung Lin, 林依蓉 |
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| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 By using solid-state reactions we have successfully synthesized six series of phosphors for vacuum ultraviolet (VUV) excitation with chemical compositions of A: Tb3+, B: Tb3+, C: Tb3+, D: Tb3+, E: Eu2+ and F: Eu2+. X-ray diffraction and electron microscopy were used to carry out phase identification and microstructure characterizations of the phosphors, respectively. Most importantly, the VUV light source (wavelength < 200 nm) and research facilities used to investigate the photoluminescence (PL) spectra, energy transfer mechanism and application evaluation of VUV phosphors are provided by National Synchrotron Radiation Research Center (NSRRC). The optimal excitation wavelength used to pump the B: Tb3+, C: Tb3+and D: Tb3+ phosphors to generate strong but narrow yellowish-green luminescence, attributed to 5D4→7F5 transition of Tb3+, has been found to be 172 nm. These observations can be rationalized by the presence of PO43- or BO33- anionic groups in the host that generally show strong absorption in the VUV range. In addition, the enhanced luminescence intensity can also be attributed to the overlapping of absorption peaks between host and Tb3+ that is considered to improve the energy transfer efficiency from the host to the activator. However, the green-emitting VUV phosphor A: Tb3+ was found to exhibit weaker luminescence, which was attributed to poor VUV absorption of the host matrix. Furthermore, the broad green luminescence observed in both E: Eu2+ and F: Eu2+ is attributed to the emissive 4f65d1→4f7 transition. However, the observed reduced PL intensity has been attributed to the poor host absorption of VUV radiation and/or the low efficiency of energy transfer between host and the Eu2+ activator. Based on the analysis on the microstructure of the six series of VUV phosphors, we found that, among the phosphors investigated, D: Tb3+ shows the smoothest surface morphology, the most homogeneous grain size distribution and the strongest PL intensity and relative brightness that were found to be comparable with those of commodity phosphors. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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