Thermoelectric properties of a cubic quasicrystalline approximant in Al-Cu-Ir system were investigated experimentally and theoretically. A homogeneous sample with no secondary phase was synthesized using an arcmelting and a sparkplasmasintering processes followed by heat treatment at 1173 K, and its thermoelectric properties were measured at temperatures between 373 K and 1023 K. Theoretical calculations of the thermoelectric properties were performed under three different approximations, i.e., constantrelaxationtime, constantmeanfreepath, and constantdiffusioncoeffi cient approximations, for the energy dependence of the relaxation time of the electrons. The experimental Seebeck coeffi cient was well reproduced, and physically acceptable lattice thermal conductivity was estimated only under constantdiffusioncoeffi cient approximation for the present material. Thermoelectric fi gure of merit zT of the present sample was lower than 01, and the maximum value of zT ≈ 03 achievable by electron doping was predicted by the theoretical calculation under the rigidband approximation.

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We present a stable simple cubic structure in the quaternary system (Al-Si)-Cu-Fe with the composition Al 55 Si 7 Cu 25.5 Fe 12.5 which corresponds to the p/q = 1/1 cubic approximant of the icosahedral Al-Cu-Fe phase. This cubic structure, with lattice parameter a = 12.330 Å and density ρ ≈ 4.773 g cm −3 , contains roughly 135 atoms per unit cell. Preliminary studies of NMR and ME spectra as well as electric conductivity properties strongly suggest that this alloy shares most of the basic structural and physical properties of the parent icosahedral phase I-(Al-Cu-Fe). † This is used to define the orientation of the 3D cut space in the standard 6D space representation of the quasicrystal.