This study indicate that the chemical inter-diffusion between the Cr-doped glass/glass ceramic and quartz (SiO2) influence the fluorescence properties of glass, mainly because of Cr4+ replacing by tetrahedral of Si4+. Cr4+ fluorescence intensity was reduced and its emission band was shifted to longer wavelength (red shift). We selected the SiO2-based glass composition: Mg2SiO4 glass-ceramic and reduced a ratio of SiO2 sintered into the ceramic powder. This paper used diffusion characteristics of quartz (SiO2) to compensate for reduced SiO2 in the ceramic powder. After diffusing with quartz (SiO2), ceramics powder changed into glasses. The intensity of fluorescence and the crystal field had been improved. The center of Cr4+ fluorescence is about 1100nm belonging to Cr4+:Mg2SiO4 crystal. The ratio of Cr4+ in Mg2SiO4 crystal/Cr4+ in MgO-SiO2 glass increases from 0.33 to 1.74. The goal is to develop a novel glass which is resistant to SiO2 inter-diffusion degradation during fiber fabrication, and provide the new fiber technology to avoid the influence of inter-diffusion This study provides new types of treatment: Laser induced crystallization. Laser heat-treatment can more quickly induce crystals in glass during seconds, than traditional heat-treatment which require several hours. This study also indicate that one step laser heat-treatment induce micro-crystals, but one step laser heat-treatment induce nano-crystals. We successfully produced nano-crystallization during seconds.

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The photocatalytic wastewater treatment facility presented in this thesis is a promising economic green technology that can degrade wastewater’s organic and ammonia pollutants, which produce environmentally sensitive products like CO2, H2O, Nitrates, etc. that can be captured and used in many biological and engineering ways. Previous advances used for this research was determining the importance of cleaning the photocatalytic nanocrystals, Fe-TiO2, as one of the revolutionary improvements that expose and maximizes the active surface of the photocatalytic nanocrystals to the pollutants enabling the strong oxidants produced by the absorption of a photon, excitation of an electron and positive hole to produce oxidants on the surface of the nanocrystals. The oxidants indiscriminately produce CO2 and H2O from living and non-living organic matter to obtain near ~100% clean water. This research focused on taking the next steps in the development of a wastewater cleaning facility tested in our laboratory. An important step involved coating Fe-TiO2 crystals onto flexible, strong, fiber-glass cloth using a sol-gel processing method. Success was found in this research by applying the coated fiberglass cloth into a photoreactor aimed to clean a large amount of water rather than the laboratory scale. / Graduate

Transparent glasses embedded with TTB structured ferroelectric nano/micro crystals (K3Li2Nb5O15, Ba5Li2Ti2Nb8O30) were fabricated in various tellurite and borate based glass matrices and characterized for their physical properties. Nanocrystals of K3Li2Nb5O15 were successfully grown inside tellurite glass matrix via conventional heat-treatment route. Eventhough, tellurite glasses preferentially crystallize only on the surface, bulk uniform crystallization was achieved in the (100-x) TeO2 - x(1.5K2O-Li2O-2.5Nb2O5) system. Heat capacity studies revealed them to be thermodynamically less fragile than any other tellurite glasses ever reported in the literature. Pyroelectric and ferroelectric effects as well as second harmonic generation were demonstrated for the heat treated (glass nanocrystal composites) samples in this system. The conventional method of melt-quenching of constituent oxides could not yield Ba5Li2Ti2Nb8O30 crystallites. So, Ba5Li2Ti2Nb8O30 microcrystals were successfully formed in tellurite glass matrix by mixing pre-reacted Ba5Li2Ti2Nb8O30 ceramic powders with TeO2. The glass transition temperature was found to be the highest ever reported and this system was kinetically strong based on the fragility parameter. Dielectric studies revealed a frequency and temperature independent nature of the dielectric constant and very low dielectric loss. The SHG measurement which was carried out as a function of temperature demonstrated the incidence of blue second harmonic generation in the microcrystals present in the glass matrix. Ba5Li2Ti2Nb8O30 nanocrystals were successfully crystallized in the transparent glass system (100-x)Li2B4O7 – x(Ba5Li2Ti2Nb8O30). Dielectric constant increased while the dielectric loss decreased with the increase in Ba5Li2Ti2Nb8O30 content. Nuclear magnetic resonance spectroscopic studies were carried out to have an insight into the structure of this system. Transmission studies and refractive index measurements were performed and various optical parameters were calculated. Dielectric and transport properties were studied for the glasses and glass nano/microcrystal composites of all the systems reported in this thesis. Li+ ion was found to be responsible for conduction in all these systems. Evolution of self-organized nanopatterns of K3Li2Nb5O15 crystals has been demonstrated in the glass system (100-x) TeO2 - x(1.5K2O-Li2O-2.5Nb2O5) by excimer laser irradiation. The second harmonic signal observed by the Maker fringe technique has been attributed to the presence of well-aligned nano-sized grating structures in the glass system. Glasses belonging to the systems TeO2-K3Li2Nb5O15, TeO2-Ba5Li2Ti2Nb8O30 and V2Te2O9 undergo spinodal decomposition on exposing to KrF pulsed excimer laser. The spinodally phase separated structures were observed on all the surfaces of the samples. Ring shaped patterns were observed on several locations of the samples at higher frequency of laser pulses probably owing to the shock waves produced by the high intense laser beam. Line shaped patterns were found to originate on the sample surfaces when irradiated for longer periods.