Study on the Structural Relaxation in Supercooled Liquids and Glasses

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The structural relaxation in the super cooled liquid and glass states has been studied in present project. The glass forming systems of chlorides and oxides has been selected as the objects. Ultrsonic spectroscopy has been carried out in binary systems containing zinc chloride. In those binary melts, the dispersion of sound wave has been found in the super cooled temperature region.Rayleigh-Brillouin scattering experiment has been carried out for ZnCl_2-NaCl, ZnCl_2-KCl and ZnCl_2 ZnCl_2-CsCl binary melts. The complete profiles of Rayleigh-Brillouin spectra were obtained for each binary melt, and at temperatures ranging from 550 to 1000K.The remarkable change in the shape of the spectrum with the variations in temperature and composition has been observed and has been concluded to be due to a structural relaxation in the melts. A dispersion of sound wave propagation was observed in the melts at the hypersonic region. The spectra have been analyzed by the viscoelastic theory with the assumption of the single relaxation. The relaxation time and the velocities at limiting low frequency and high frequency were determined as functions of temperature and of alkali chloride composition.The experiment has also been done for glass state. The samples of pure ZnCl_2, ZnCl_2-KBr and ZnCl_2-KI has been used for preparing glass samlpes. The spectra obtained in glass state was similar to those in super cooled liquids. In the glass state there was not structural relaxation in the frequency region of GHz.