| Summary: | 碩士 === 國立清華大學 === 物理學系 === 98 === Abstract
Lanthanide doped semiconductors have attracted great interest due to potential applications in photoelectric devices and optical communications, as well as excellent mechanical, thermal and anticorrosive properties.
To study the physical properties of Tb-doped titanium dioxide nanoparticles, a series of samples have been synthesized by using sol-gel method under different preparation conditions (dopant concentrations and acidic catalyst). XRD patterns, TEM images, EXAFS analysis and PL、PLE spectra were used to characterize TiO2:Tb nanoparticles. As revealed by XRD, the average particle size of the samples appears to decrease with increasing Tb3+ concentration. On the other hand, the phase transition temperature increases with Tb3+ concentration. Both are attributed to the formation of Tb-O-Ti bond on the surface of titanium dioxide particles. Because the ionic radius of Tb3+ is larger than that of Ti4+, Tb can hardly substitute for the Ti4+ sites. Instead, Tb-O-Ti bonds are formed on the surface and therefore restrain the crystallite growth and phase transformation. In order to offer proof of this speculation, the local structure of Tb ions has been studied by EXAFS analysis, and Tb-O-Ti bonds were directly observed.
Observation of a peak at 378nm in the PLE spectra and the same trend of variation in the photoluminescence spectra of the host (broad band from 400nm to 700nm) and dopant (characteristic lines at 486nm, 543nm, 581nm, and 616nm) as the nitric acid concentration is changed in the sol-gel process are considered as strong indication of energy transfer between host and terbium.
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