Ultrasonic study of hydrogen motion in a Ti-Zr-Ni icosahedral quasicrystal and a 1/1 bcc crystal approximant

Ultrasonic attenuation measurements have been performed on the Ti-Zr-Ni alloy system over the temperature range 35-335 K. Both a multigrained icosahedral quasicrystal and a 1/1 bcc polycrystalline approximant were studied. The alloys were hydrogenated to a hydrogen to metal ratio of 0.79 for the icosahedral phase and 0.20 for the crystalline phase. Temperature-dependent attenuation peaks were observed in the alloys loaded with hydrogen while the hydrogen-free materials showed no unusual features. For measurement frequencies near 1 MHz the attenuation maxima occurred near a temperature of 250 K for the crystalline phase and 220 K for the icosahedral phase. The results imply that the hydrogen motion is about one order of magnitude faster in the icosahedral phase than in the approximant phase. Whether this result is due to an intrinsic difference between the two Ti-Zr-Ni phases or to a dependence on hydrogen concentration cannot be determined from the present measurements.