ON THE SOLUBILITY OF ALUMINUM IN THE INTERMETALLIC COMPOUND COGA3

The gallium atomic positions in the intermetallic compound CoGa3 (Pear son Symbol tP 16, space group P4(2)/mnm) can be occupied by aluminium up to x(Al)=0.35. Lattice parameters were measured in the whale homoge neity range of CoAlxGa3-x. Both the axial ratio cia and the unit cell volume decrease with increasing aluminium content. The extrapolated av erage atomic volume for the hypothetical phase 'CoAl3 with CoGa3 struc ture' is significantly higher than the average atomic volume of the ob served non-defect cobalt/aluminium-containing structure occurring near the stoichiometry CoAl3-o-Co4Al13 (oP102, o-Co4Al13 type). The measur ed data of the pseudoternary phase CoAlxGa3-x are compared with data f or the other gallium-containing representatives of the CoGa3 structure type. (C) 1997 Elsevier Science S.A.