Anisotropic Transport Properties of the Orthorhombic Al13Co4 Approximant to the Decagonal Quasicrystal

Anisotropic transport properties (electrical resistivity, thermoelectric power, Hall coefficient and thermal conductivity) of the o-Al13Co4 orthorhombic approximant to the decagonal phase were investigated. The crystalline-direction-dependent measurements were performed along the a, b and c directions of the orthorhombic unit cell, where (b, c) atomic planes are stacked along the perpendicular a direction. Anisotropic electrical and thermal conductivities are the highest along the stacking a direction. The anisotropic thermoelectric power changes sign with the crystalline direction and so does the anisotropic Hall coefficient, which changes from the negative electron-like to the positive hole-like for different combinations of the electric current and magnetic field direction. The transport properties of the o-Al13Co4 phase were compared to the literature data on approximant to the decagonal quasicrystals, the Al76Co22Ni2 and the Al80Cr15Fe5, allowing for the study of evolution of transport properties with increasing structural complexity and unit cell size.