M\"ossbauer Spectroscopic and XRD Studies of two eta-Fe2Al5 Intermetallics

TL;DR

This study investigates two eta-Fe2Al5 intermetallic compounds using Mössbauer spectroscopy and XRD, revealing differences in atomic dynamics, site occupancy, and vibrational properties related to their stability boundary.

Contribution

It provides detailed vibrational and structural analysis of eta-Fe2Al5 alloys, highlighting the effects of Al content on atomic dynamics and phase stability.

Findings

Fe atoms exhibit harmonic vibrations across temperatures.

Al atoms show strong anharmonicity.

Differences in vibrational properties linked to alloy stability.

Abstract

Two intermetallic FeAl compounds with Al content of 70.68 and 72.17 at.pct were studied using M\"ossbauer spectroscopy (5 to 296 K) and X-ray diffraction (15 to 300 K). The compounds were found to crystallize in the orthorhombic Cmcm space group (eta-phase). The collected data revealed that dynamics of the Fe atoms (harmonic in entire temperature range) is significantly different that Al atoms. For the latter strong anharmonicity was evidenced. Moreover, it was found that partial filling of the different Al sites leads to occurrence of low and high symmetry coordination of Fe atoms, which was reflected in occurrence of two distinct doublets in M\"ossbauer spectra. All spectral parameters of the doublets as well as the Debye temperature, force constant, kinetic and potential energies of vibrations were determined. Those results revealed significant differences between both alloys, likely originating from approaching the stability boundary of the eta-phase for Fe-Al 72.17 at.pct alloy.