The CaAg2—CaZn2—CaAl2 pseudo ternary system: crystal structures and structural stability

Abstract

The CaAg2—CaZn2—CaAl2 pseudo ternary system has been studied by micrographic and X-ray diffraction analyses of 37 alloys, melted and annealed at 973 K or 873 K in tantalum crucibles. Single crystal and powder X-ray data show a distribution of the phases among four structure types: MgCu2, MgZn2, MgNi2 (the Laves phases) and CeCu2 (for the first time reported for KHg2). A good separation of the structural domains was obtained by means of a two-dimensional map based on the size and electronic factors. The different volume effects shown by the CeCu2-type phases as regards those of the Laves phases were accounted for on the basis of the hard-sphere space filling model.