Thermal and thermoelectric properties of icosahedral Al62Cu25.5Fe12.5 quasicrystal

Experimental results on thermal and thermoelectric properties of icosahedral i-Al62Cu25.5Fe12.5 quasicrystal in temperature range 4.2–340 K are examined, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal is made. The results of thermoelectric properties can be consistently explained by a two-band model. Although the picture that overlaps with the valence and the conduction bands at Fermi level is responsible for the coexistence of both types of carriers enables us to describe quasicrystals as semi-metals, the situation in which temperature variation of the electrical conductivity is determined by that of carrier density is essentially the same as in the case of normal semiconductor. The phonon thermal conductivity increases monotonically with temperature showing a shallow maximum at about 25 K, followed by a minimum around 70 K, and a subsequent increase. The shallow maximum in phonon thermal conductivity could be interpreted as a crossover from the regime of a dominant scattering on tunneling states of an unspecified nature to the regime where quasiperiodic Umklapp processes are important.