Ultrasonic Attenuation and Dislocation Damping in Crystals of Ice

抄録

The attenuation of megahertz ultrasound has been measured in single crystals of ice at higher temperatures. Specimen crystals were grown by the Bridgman method from purified water, and crystals doped with various ions were also used. An overdamped resonance peak of dislocation damping always appeared in decrement-vs-frequency, and the peak frequency was shifted by the temperature change and by the Na-ion doping. It was also found that the attenuation value increased very rapidly with large fluctuation when the temperature approached the melting point, and that the temperature dependence of attenuation was sensitive to the ion doping. Experimental data were consistently analyzed on the basis of the vibrating dislocation model with the following conclusions: Dislocations are pinned by impurity ions (Na⁺) through an elastic interaction between the two kinds of defects; the damping constant for the dislocation vibration is of the order of 10⁻⁴ cgs; the density of grown-in dislocations is around 10⁶ cm⁻²; the dislocation density rapidly increases as [1−(T⁄T_melt)]⁻¹ near the melting temperature.