Electrical resistivity of crystal approximants in Sc-based alloys

Abstract

Electrical resistivity and specific heat have been investigated for MI-type 1/1 crystal approximant phases in binary Sc–M (M = Ru, Rh, Ir and Pt), and ternary Sc–Rh–Ti and Sc–Rh–Au alloys. The electrical resistivities of the binary phases are relatively low and show small positive temperature coefficients, in contrast to the MI-type ternary 1/1 phases which often exhibit large negative temperature coefficients. The electronic specific heat coefficients of the binary Sc–M phases are considerably large, consistent with the low electrical resistivity. The Debye temperature of the binary Sc–M phases increases with increasing atomic mass of the M element, which could be attributed to the increase in the covalent nature of the atomic bonds in the icosahedral clusters. In the ternary Sc–Rh–Ti system, the temperature coefficient of resistivity increases with increasing Ti concentration. On the other hand, the addition of Au decreases the temperature coefficient of resistivity and changes the sign to negative at 8 at% Au in the case of the Sc–Rh–Au system.