Study on structural relaxation in silica glass

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Investigations of structural relaxation in silica glass are necessary for developing silica glasses with high performances such as ultralow-loss and UV-proof properties. Silica glass is also advantageous for studying on glass transition mechanism because of its simple structure. In this project we tried to measure various properties of silica glasses over a wide-temperature range including the glass transition temperature, and have elucidated structural relaxation processes and their impurity effects as follows :(1)OH or Cl enhances the alpha-relaxation governed by viscous flow, and also generates a sub-relaxational process.(2)he sub-relaxational process is local structural change caused by impurity diffusion.(3)I restrains the alpha -relaxation, contrary to OH and Cl.From these results, we have established controlling the structural relaxation by impurity doping, and developed the following high-functional silica glasses.(1)Na-doped ultralow-loss glass(2)l-doped ultra-heat-proof glass(3)Ultra UV-proof glass created by OH doping, UV-laser irradiation, and thermal annealing