STUDY OF THE INTERACTION OF PT AND RH WITH NB OR TA

The 1100 degrees C isothermal sections of the Pt-Rh-Nb and Pt-Rh-Ta sy stems are plotted using the complementary diffusion couple technique a nd studies of equilibrated alloys. No ternary phases were found in eit her system. The phases belonging to different structural polytype fami lies exhibit polytypic behavior in the classical sense and some phase fields could not be resolved. The binary phases with more multilayered structures dissolve more of the third component than their simpler an alogs. Also, the phases with structures belonging to the same family t end to have more complicated packings the greater their deviation from the ideal stoichiometry.