High-temperature specific heat of quasicrystals and a crystal approximant

Abstract

Specific heat measurements have been performed by DSC in the temperature range from 430 to 1080 K for an icosahedral quasicrystal of Al–Pd–Mn, a decagonal quasicrystal of Al–Cu–Co and a crystal approximant of Al–Pd–Fe. The measured specific heat per atom at constant pressure c p( T) has been converted to that at constant volume c v( T) by use of the data of bulk modulus previously reported and the data of the thermal expansion coefficient which we measured by dilatometry. c v( T) of all three samples stay at around 3 k B up to about 700 K, as expected from Dulong–Petit's law. For the two quasicrystals, however, c v( T) increases dramatically and reaches 4.7 k B at 1080 K. In contrast, the deviation in c v( T) of the crystal approximant is small; it is about 3.6 k 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 light of thermal excitation of phasons.