Moessbauer Diffractometry on Chemical Sites of 57Fe in Fe3Al

A Moessbauer powder diffractometer was used to measure diffraction patterns from polycrystalline 57Fe3Al. The intensities of Bragg diffractions were measured when the incident γ-rays were tuned to different resonances of the Moessbauer spectrum. The bcc fundamental diffractions were strong, and superlattice diffractions of (1/2 1/2 1/2) and (1 0 0) families were measurable. The 57Fe local environments with 0 Al and 4 Al first-nearest-neighbors had the periodicities expected from their sites in the perfect D03 unit cell, but the long-range periodicity of the 3 Al environment was also measured. This disordered site had a surprisingly high degree of B2 long-range order.