Alloy-oxide equilibria in the system Pt-Rh-O

Abstract

The composition of Pt-Rh alloys that co-exist with Rh₂O₃ in air have been identified by experiment at 1273 K. The isothermal sections of the phase diagram for the ternary system Pt-Rh-O at 973 K and 1273 K have been computed based on experimentally determined phase relations and recent thermodynamic measurements on Pt_1-X Rh_X alloys and Rh₂O₃. The composition dependence of the oxygen partial pressure for the oxidation of Pt_1-X Rh_X alloys at different temperatures, and temperature for the oxidation of the alloys in air are computed. The diagrams provide quantitative information for optimization of the composition of Pt_1-X Rh_X alloys for high temperature application in oxidizing atmospheres.