The antimony-iron-zirconium (Sb-Fe-Zr) system

Phase equilibria were established in the Fe-Sb-Zr ternary system below 60 at. % Sb for an isothermal section at 800 degrees C; the very Sb-rich region was studied at 600 degrees C. Investigation of the phase relations was based on light optical microscopy, electron probe microanalysis, and X-ray diffraction experiments on are melted bulk alloys, which were annealed up to 350 h, Three ternary compounds were observed: ZrFe(1-x)Sb (0.3 < x < 0.5; defect TiNiSi type), Zr(6)Fe(1-x)Sb(2+x) (0 < x < 0.24; ordered Fe(2)P type) and Zr(5)Fe(x)Sb(3-x) (x = 0.44; W(5)Si(3) type). Whereas Zr(5)Fe0.44Sb(2.56) at 800 degrees C formed at a given composition without a significant homogeneity region, a rather extended solid solution up to about 9 at,% Sb was observed for the Laves phase Zr(Fe(1-x)Sb(x))(2-y). At 800 degrees C, binary ZrFe(2-y) was only observed with the cubic MgCu(2) type; Sb content of more than about 3 at, % Sb stabilized the hexagonal MgNi(2) type in the Zr-poor end of the homogeneity region. The MgCu(2) type prevails at higher Sb content of up to 9 at. % Sb at the Zr-rich side. Zr(3)Sb (Ni(3)P type) seems to dissolve up to 3.5 at. % of Fe replacing Zr in the structure. Binary Zr(5)-Sb(3+x) (Ti(5)Ga(4) type or filled Mn(5)Si(3) type) dissolves up to 11 at. % Fe by gradually replacing the Sb atoms in the octahedral sites with Fe; thus the boundary of the homogeneous region on the Fe-rich side essentially corresponds to the ternary limit at Zr(5)FeSb(3), For stoichiometric binary Zr(5)Sb(3) the authors observed only a small solubility (<1 at,% Fe) with the Yb(5)Sb(3) type. At 800 degrees C there is practically no solid solubility of Zr in the iron antimonides and of Fe in the zirconium antimonides richer than 40 at. % Sb.