PHASON RELAXATION MECHANISMS IN AL-PD-MN SINGLE-QUASI-CRYSTALS

Quasicrystals represent a new state of condensed matter which exhibits long-range quasiperiodic translational order and orientational order with noncrystallographic symmetry. Mechanical spectroscopy was applied for the study of defect properties in stable icosahedral single-quasi crystalline Al-Pd-Mn samples. Two mechanical loss maxima appear at 360 K and 870 K for a measuring frequency of f approximate to 3 Hz. The r elaxation parameters for both peaks were determined as H = 0.98 eV, ta u(infinity)(-1) = 4.5 . 10(14)s(-1) for the low temperature peak, and H = 4.0 eV, tau(infinity)(-1) = 3.0 . 10(24)s(-1) for the high tempera ture peak, respectively. Both peaks are related to phason defects whic h are characteristic for the quasicrystalline structure.