High-temperature specific heat of quasicrystals and a crystal approximant

Specific heat measurements have been performed by DSC in the temperature ra nge from 430 to 10SO K for an icosahedral quasicrystal of Al-Pd-Mn, a decag onal quasicrystal of AI-Cu-Co and a crystal approximant of Al-Pd-Fe. The me asured specific heat per atom at constant pressure c(p)(T) has been convert ed to that at constant Volume c(v)(T) by use of the data of bulk modulus pr eviously reported and the data of the thermal expansion coefficient which w e measured by dilatometry. c(v)(T) of all three samples stay at around 3k(B ) up to about 700 K, as expected from Dulong-Petit's law. For the two quasi crystals, however, c(v)(T) increases dramatically and reaches 4.7k(B) at 10 80 K. In contrast, the deviation in c(v)(T) of the crystal approximant is s mall; it is about 3.6k(B) at 1080 K. The origin of the large deviations in c(v)(T) of the quasicyrstals from Dulong-Petit's value is discussed in ligh t of thermal excitation of phasons. (C) 2001 Elsevier Science B.V. All righ ts reserved.