The lattice spacing relationships in H.C.P. ϵ and η phases in the systems Cu-Zn, Ag-Zn; Au-Zn and Ag-Cd☆

Abstract The lattice spacings of the h.c.p. ϵ and η phases in the systems Cu-Zn, Ag-Zn, Au-Zn and Ag-Cd have been studied by the X-ray powder method. The relationship between the obtained data for the ϵ and η phases and the lattice spacings of both the cubic α phases (primary solid solutions) based on the noble metals and the h.c.p. ζ phases are discussed in the light of previous similar investigations. It is suggested that the various trends in the changes of the lattice spacings when plotted as a function of the electron concentration may be interpreted in terms of the interactions between the Fermi surface and the Brillouin zone. In particular it is proposed that overlap of electrons across the {00.2} faces of the zone takes place in the ϵ phases near Zn- or Cd-rich boundaries at electron concentration values between 1.8 and 1.9. The nature and magnitude of the band gaps in the Brillouin zone, and other factors which may influence the axial ratio, are also discussed.