| The study of this thesis is about TiO2 nanocrystals, which are obtained by first sol, hydrothermal and annealing at different temperature, from 300 oC to 900 oC (step 100 oC). The structure and luminescence properties of TiO2:Er3+ nanocrystals are characterized by XRD, SEM, RAMAN, and luminescence spectra under 325nm, 488nm, and 980nm excitation.The content of the paper is about the structure and luminescence properties of TiO2:Er3+ nanocrystals and their relationships. By XRD, with increasing the doped erbium concentration, the nanocrystalline size for anatase TiO2 is reduced. Below annealing temperature 800 oC, TiO2:Er3+ nanocrystals exhibit anatase structure, and the size of them increases with increasing the annealing temperature. However, at annealing temperature 800 oC, a structure of pyrochlore Er2Ti2O7 evolves from interface/surface on anatase. The anatase phase disappears at annealing temperature up to 900 oC and the rutile phase becomes dominant. 800 oC and 900 oC are respectively the former and later transformation temperature. The RAMAN spectra also prove the occurrence of the transformation. The modes of anatase exit in RAMAN spectra at annealing temperature 800 oC, and the modes of rutile at 900 oC.With increasing annealing temperature from 300 oC to 800 oC, the Eg mode from TiO2:Er3+ nanocrystals has red shift, but other modes: B1g, A1g/B1g, and Eg do not shift. Comparing with them, the modes of the bulk, TiO2:Er3+ does not shift. We employ UV 325nm, visible 488nm and IR 980nm lasers to excite TiO2:Er3+ for comparing with the relationship between the luminescence and the structure at various annealing temperatures. We have analyzed these spectra. We find that the luminescence spectra drastically change when transformation occurs, following 325nm, or 980nm, or 488nm irradiation. This change is more than our expectation and is rarely reported. This is ascribed to the transformation of structure, resulting...
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