STRUCTURAL AND MOSSBAUER STUDIES OF THE ALLOY SYSTEM FEAL1-XNBX

X-ray diffraction and Mossbauer spectroscopy results of the system FeA l1-xNbx show that the cubic (CsCl) FeAl phase dominates for small valu es of x, and persists as x increases, but also, the hexagonal (C14) Fe 2Nb phase develops. The values of the lattice constants and Mossbauer hyperfine parameters indicate that both phases contain impurities, i.e ., the phases are FeAl(Nb) and Fe2Nb(Al). The Debye temperature THETA( D) for the FeAl phase is derived from the intensity analysis of the di ffraction lines and a value of (385 +/- 5) K is obtained. This is near ly equal to the Debye temperatures for alloys of Fe and Nb. This resul t is also supported by the fact that the relative Mossbauer absorption intensities corresponding to the two phases remain constant as the te mperature is lowered down to 85 K. The absence of magnetic hyperfine s plittings in Mossbauer spectra indicate that both phases of the alloy system remain paramagnetic down to the LN2 temperature.