Y-Fe-Al ternary system:: partial isothermal section at 1070 K Powder X-ray diffraction and Mossbauer spectroscopy study

Phase equilibria were established in the Y-Fe-Al ternary system within the concentration region 50-100 at.% Al for an isothermal section at 1070 K by means of scanning electron microscopy and powder X-ray diffraction, Two ternary aluminides were observed, YFexAl12-x (4 less than or equal tox less than or equal to5.6) with the ThMn12-type structure, a = 8.6467(9)-8.7603(7) Angstrom, c = 5.0374(6)-5.0504(5) Angstrom and YFe2Al10, YbFe2Al10-type strucrure, a = 8.9649(6) Angstrom, b = 10.1568(6) Angstrom, c = 9.0113(6) Angstrom. The only binary which forms a prolonged solid solution range is YAl2. The unit cell edge of the YFexAl2-x compounds, MgCu2-type structure, decreases with Fe content from 7.834(9) Angstrom for x = 0 down to 7.689(4) Angstrom for x = 0.5. Fe-57 Mossbauer spectroscopy data of YFe2Al10 show an unusually large isomer shift for Fe in Al-containing intermetallics and confirm that no magnetic ordering occurs down to 5 K. (C) 2001 Elsevier Science B.V. All rights reserved.