57Fe Mِssbauer study of icosahedral Al55Si7Cu25.5Fe12.5 and its 1/1 approximant

The icosahedral Al55Si7Cu25.5Fe12.5 alloy and its 1/1 approximant of the same composition have been studied with 57Fe Mössbauer spectroscopy (MS) in the temperature range 4.4–473.2 K. The average quadrupole splitting decreases with temperature as T3/2 for both alloys and its value is significantly larger for the icosahedral alloy. The vibrations of the Fe atoms in both alloys are well described by a simple Debye model, with characteristic Mössbauer temperatures of 454(22) and 491(25) K for the icosahedral and approximant alloys. The local properties measured by zero-field 57Fe Mössbauer spectroscopy are insensitive to the different nature of the long-range order, quasicrystalline vs. crystalline, in the investigated alloys.