Effect of Iridium and Rhodium on High-Temperature Volatilization Behavior of Platinum Alloys

This study investigated the volatilization behavior of platinum–rhodium–iridium (Pt–Rh–Ir) ternary alloys at high temperatures ranging from 1273 K to 1673 K, for periods of 0, 24, 48, 73 and 96 h. The high-temperature volatilization properties of the alloys were evaluated by weight loss measurements and by observing microstructural changes. The results revealed that high-temperature volatilization of the platinum alloys preferentially occurred near the grain boundaries. The high temperaturevolatilization was accelerated when iridium was added to platinum but suppressed when rhodium was added to the platinum–iridium (Pt–Ir) alloy. This could be explained by the fact that the vapor pressure of iridium oxide is greater than that of platinum oxide, while the vapor pressure of rhodium oxide is lower.