الفهرس 
Introduction And Literature SurveyOnly 14 pages are availabe for public view
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Abstract
The purpose of the present work is to study some of the spectroscopic and physical properties of Silica–titania (SiO2–TiO2) nano-composite doped with some rare earth elements (Ho3+ and Yb3+) ions in the monolith and thin film form. The samples have been prepared using sol-gel technique to reach the best composition with superior optical properties and up-conversion emission spectra in order to be suitable for laser applications, solar cell, wave guide and photocatalyst.
This thesis is divided in to four chapters in addition to list of tables, list of figures and references.
Chapter one: Is devoted to the introduction, which discuss the important of SiO2 –TiO2 nano-composite pure and doped with some rare earth elements. The compounds are receiving great interest in scientific research due to their physical and spectral properties. It also includes overview of the literature survey of pure and co-doped SiO2–TiO2 nano-composite with Ho3+ and Yb3+ ions; from their structure, spectroscopic and physical properties.
Chapter two: Includes the theoretical concepts of physical and spectroscopic properties for SiO2–TiO2 nano-composite crystalline compounds.
Chapter three: Includes samples preparation using a modified sol gel method and characterization techniques used for investigated the samples such as XRD, Raman spectroscopy, FTIR, FESEM, EDX, UV/VIS/NIR spectrophotometer and finally photoluminescence spectrophotometer.
Chapter four: This chapter includes results and discussion of structure, morphology, optical and photoluminescence for SiO2–TiO2 nano-composite as host material which co- doped with different concentrations of (Ho3+&Ho3+:Yb3+) ions in two main sections:
Section(I):
Studied SiO2–TiO2 nano-composite in the monolith form doped with Ho3+ ions (0.4, 1, 1.4) mol% annealed at 500,800 and 1000°C for 3 hours. from XRD results all samples formed in tetragonal nano-composite shape. It is observed that mixed low intensity crystalline phases of a little bit amount anatase and rutile which decrease by increasing the Ho3+ ions content and reached its maximum intensities at 500oC. where these lower annealing temperature at 500oC, are not enough for completely transformation from anatase to rutile phase. Further increase in temperature up to 1000oC causes pre-crystallization and transformation of amorphous silica to α-crystobalite tetragonal silica in pure sample, while in doping samples transformation from anatase to rutile phase their intensities decreased by increasing the Ho3+ ions concentration.
The results show an increase in crystallite size from 16 up to 38 nm by increasing the annealing temperature. So the lower Ho3+ ions concentration at 0.4 mol% can be considered as the optimized concentration for using it in co-doping with0.5, 0.75 and 1 mol % of Yb3+ ions. from XRD ST0.4H0.5YM, ST0.4H0.75YM and ST0.4H1YM samples annealed 500,800 and 1000oC are formed in nano-composite tetragonal shape. Increasing Yb3+ ions concentration induced the crystallite size due to substitution with Yb3+ ions, with larger ionic radii which could causes internal stress in the crystal and then the size deceases; [Ho3+=0.9Å, Yb3+=.87Å and Ti4+=0. 61Å].
FTIR spectra of prepared samples show an absorption band appeared at 952cm-1 assigned to Si–O–Ti vibration mode. The appearance of this band confirmed strong interaction between titania and silica at molecular scale. By arising the annealing temperature up to 1000 ̊C, the bands appeared at 3368 and 1637 cm-1 which referred to absorbed water is disappeared. Also the intensity of Ti-O absorption band crystalline TiO2 at 444 and 793 cm-1 increase with increasing annealing temperature especially in the doping samples. This indicates that the numbers of Ti-O-Ti vibrations are also growing with increasing annealing temperature, which agrees well with XRD analysis