Atomic structure and electron transport properties of the Al–Pd–Mn–Re–Si 1/1-cubic approximant

Abstract

The formation area of the Al–Pd–Mn–Re–Si 1/1-cubic approximant (1/1-AC) was determined by partially substituting Re for Mn in the Al–Pd–Mn–Si 1/1-AC. It was found that the Al–Pd–Mn–Re–Si 1/1-AC is stabilized at compositions expressed by the formula Al_{67−0.125 x} Pd_{11+0.375 x} Mn_{14−1.25 x} Re _x Si₈ with Re concentration x < 5 at. %. Synchrotron radiation Rietveld analysis was performed on the approximants to investigate the mechanism determining the formation range of the 1/1-AC. Re atoms were found not to be substituting for all Mn atoms but only those in limited sites. This selection rule for the Re substitution is caused by the 10% larger atomic radius of Re than that of Mn. The importance of the size effect of the constituent elements is strongly suggested for stabilizing quasicrystals and approximants.