Evaluation of Oxide Dispersion Strengthened Palladium for Platinum/Palladium Thermocouples

Type R and S thermocouples are widely used not only for industrial temperature measurement but also for temperature standards. These types of thermocouples contain rhodium in the positive branch, so it is commonly known that oxidation occurs during high temperature operation and causes thermal electromotive force (E.M.F.) drift. In these days, Platinum/Palladium(Pt/Pd) thermocouple is occasionally substituted for type R and S because those are made of pure metals only and show more stability of thermal E.M.F.. However, metal grain growth occurs on pure metals at high temperature operation, and creep rupture occurs even with relatively lower stress. Especially, the melting point of palladium is lower than that of platinum, thus palladium has a tendency to creep easily at high temperature rather than platinum. We applied the Oxide Dispersion Strengthened (O.D.S.) technique on palladium in the negative branch of Pt/Pd thermocouples for further product improvements.