Thermodynamic Modeling of Equilibrium Subsolidus Phase Relations in the Ag–Pd–O 2 System

From literature values of the thermodynamic activity of Pd in Ag/Pd solid solutions and the Gibbs free energy of formation of PdO as a function of temperature, subsolidus equilibrium phase relations in the Pd–Ag–O 2 system have been calculated and compared to results from high‐temperature XRD analyses. The developed model takes into account the nonideal activity of Pd in Ag/Pd solid solutions and confirms that increasing the Ag/Pd ratio or decreasing the oxygen activity decreases the temperature at which PdO reduces. It also accurately predicts that the temperature range over which the PdO reduces is broad for Ag‐rich compositions, and narrow for Pd‐rich compositions.