Slow dynamic properties of molten silver halides

Abstract The sound absorption has been measured for molten AgCl–AgI mixtures to investigate the relation between the dynamic properties and chemical bonding. The sound absorption for molten AgI shows a large value just above the melting temperature, and decreases with increasing temperature. The sound absorption for molten mixtures around the eutectic composition increases with temperature from the melting point, showing maximum value around 580 °C, and decreases with increasing temperature. The frequency dependence of the sound absorption for molten AgI and mixtures are also measured, and the relaxation time and relaxation strength are evaluated from the observed data by assuming single Debye-type relaxation process. The evaluated relaxation time for molten AgI is about 9.0 ns just above melting temperature and decreases slightly with temperature to about 6.4 ns at 750 °C. This relaxation time corresponds to a quite slow motion compared with the ordinary atomic one, and may suggest a structural relaxation of atomic association between ionic and covalent character. In the mixture around the eutectic region, evaluated relaxation time shows a rather complicated temperature dependence. Those values decreases slightly with temperature from the melting temperature, and have a minimum value around 600 °C, and then slightly increase with the temperature.