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

Experimental results on thermal and thermoelectric properties of icosahedra l i-Al62Cu25.5Fe12.5 quasicrystal in temperature range 4.2-340 K are examin ed, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal is made. Th e results of thermoelectric properties tan be consistently explained by a t wo-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 ca se of normal semiconductor. The phonon thermal conductivity increases monot onically with temperature showing a shallow maximum at about 25 K, followed by a minimum around 70 K, and a subsequent increase. The shallow maximum i n phonon thermal conductivity could be interpreted as a crossover from the regime of a dominant scattering on tunneling states of an unspecified natur e to the regime where quasiperiodic Umklapp processes are important. (C) 20 00 Elsevier Science B.V. All rights reserved.