Phase relations and crystal structures in the Ag-Ga system

The Ag-Ga phase diagram and the zeta-Ag2Ga<->zeta'-Ag2Ga transformation have been investigated by use of optical, scanning and transmission electron microscopy combined with X-ray powder diffraction and thermal differential analysis. On the basis of the present study a new equilibrium phase diagram for the Ag-Ga system is proposed. Only two intermetallic phases are found in the Ag-Ga system: zeta' and zeta. The compositional change of Ga in zeta' is described by replacing Ga atoms in Ib position in space group P (6) over bar 2m with Ag atoms. In alloys having 25-40 wt.%Ga, the high temperature zeta-Ag2Ga is found to decompose into a Ga-rich liquid and solid zeta'-Ag2Ga at 302 degrees C. In Ga-poor alloys (15 wt.%), the high temperature zeta-Ag2Ga is found to decompose into alpha-Ag and liquid at 611 degrees C and into cr-Ag and zeta'-Ag2Ga at 395 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.