On Friauf-Laves phases in the Zr 1− xAl xT 2, Zr 1− xSi xT 2 and Zr 1− xTi xT 2 (T ≡ Mn, Fe, Co) systems

Abstract

A large number of samples of the general composition Zr 1− x Al x T 2, Zr 1− x Si x T 2 and Zr 1− x Ti x T 2 (T ≡ Mn, Fe, Co) were prepared and investigated using X-ray diffractometry and metallography. It was found that in binary Friauf-Laves phases, ZrT 2, zirconium can be replaced by aluminium or silicon up to the compositions Zr 0.7A1 0.3Mn 2, Zr 0.7Si 0.3Mn 2, Zr 0.6Al 0.4Fe 2, Zr 0.5Si 0.5Fe 2, Zr 0.4Al 0.6Co 2 and Zr 0.6Si 0.4Co 2. In all these systems the crystal structure of the prototype compounds (the cubic MgCu 2 or the hexagonal MgZn 2 type) is preserved. In the Zr 1− x Ti xT 2 systems, continuous solid solutions were formed throughout the investigated region and their crystal structures depend on the composition and/or heat treatment. An ordering phenomenon was observed only in the Zr 1− x AL x Co 2 system, where a superstructure of the MgSnCu 4 type was formed at the composition Zr 0.5A1 0.5Co 2. The stability of these phases is briefly discussed in terms of the relative atomic sizes.