ALLOY-OXIDE EQUILIBRIA IN THE SYSTEM PT-RH-O

The composition of Pt-Rh alloys that co-exist with Rh2O3 in air have b een 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 Pt1-XRhX alloys and Rh2O3. The co mposition dependence of the oxygen partial pressure for the oxidation of Pt1-XRhX alloys at different temperatures, and temperature for the oxidation of the alloys in air are computed. The diagrams provide quan titative information for optimization of the composition of Pt1-XRhX a lloys for high temperature application in oxidizing atmospheres.