The zirconium–platinum phase diagram

Phase relationships were studied in Pt-rich, near-equiatomic Zr–Pt alloys. The composition range of the previously unreported rhombohedral compound Zr3Pt4, isomorphous with Zr3Pd4 above room temperature, extends to the Zr-rich composition Zr9Pt11 by the formation of lattice vacancies on certain Pt sites. A metastable tetragonal Zr9Pt11 compound is formed, however, when vacancy formation is inhibited. The rhombohedral structure undergoes a displacement transformation on cooling between 90 and 140 °C to a low-temperature structure that is presumably triclinic. The orthorhombic compound ZrPt is stable from room temperature to 1590 °C where it transforms to a cubic B2-type structure. Structural data are given for the compounds ZrPt, Zr9Pt11, Zr3Pt4 and Zr7Pt10, and a complete Zr–Pt phase diagram is presented.