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

Phase equilibria were established in the Fe-Sb-Zr ternary system below 60 a t. % 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 bas ed on light optical microscopy, electron probe microanalysis, and X-ray dif fraction experiments on are melted bulk alloys, which were annealed up to 3 50 h, Three ternary compounds were observed: ZrFe1-xSb (0.3 < x < 0.5; defe ct TiNiSi type), Zr6Fe1-xSb2+x (0 < x < 0.24; ordered Fe2P type) and Zr5Fex Sb3-x (x = 0.44; W5Si3 type). Whereas Zr(5)Fe0.44Sb(2.56) at 800 degrees C formed at a given composition without a significant homogeneity region, a r ather extended solid solution up to about 9 at,% Sb was observed for the La ves phase Zr(Fe1-xSbx)(2-y). At 800 degrees C, binary ZrFe2-y was only obse rved with the cubic MgCu2 type; Sb content of more than about 3 at, % Sb st abilized the hexagonal MgNi2 type in the Zr-poor end of the homogeneity reg ion. The MgCu2 type prevails at higher Sb content of up to 9 at. % Sb at th e Zr-rich side. Zr3Sb (Ni3P type) seems to dissolve up to 3.5 at. % of Fe r eplacing Zr in the structure. Binary Zr-5-Sb3+x (Ti5Ga4 type or filled Mn5S i3 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 Zr5FeSb 3, For stoichiometric binary Zr5Sb3 the authors observed only a small solub ility (<1 at,% Fe) with the Yb5Sb3 type. At 800 degrees C there is practica lly no solid solubility of Zr in the iron antimonides and of Fe in the zirc onium antimonides richer than 40 at. % Sb.