??THE DEFECT STRUCTURE OF (Fel - XCO)2 RE COMPOUNDS (RE = Gd AND Tb)
Keywords:
Lattice defects, (Fe.Co), RE Compounds.Abstract
Constitutional investigations of Fe-RE, Co-RE and Fe-Co-RE systems revealed that it requires an "RE" content in
excess of (Fe] - x Cox)z RE composition in orderto prepare these compounds free from the presence of phases. A comparison
of experimental and theoretical densi ties (calculated from the volumes of the unit cells) showed that the number
ofvacantTM (TM=Fe, Co or Fc--Co) sites vary from 7.5% for (Feo.32COo.6s)Pd to 2.5% in the binary Fe.Gd compound.
Likewise, there are 7.1 % such sites in (FeO.33 COO.67)Z Tb and 3.8% in the binary Coz Tb compound. Thus, it was concluded
that the defects in the lattices of these compounds, responsible for the deviation from ideal stoichiometric compositions
are vacancies on Fe and Co sites in respective binary compounds and on Fe+Co sites in ternary compounds.
