New Structures for Jewelry Applications in Palladium

An intriguing intermetallic structure with 8:1 stoichiometry was discovered in the 1950s in the Pt-Ti system. Since then a handful of other Pt/Pd/Ni binary systems have been observed to exhibit this curious structure (Pt$_8$Zr, Pd$_8$Mo, Ni$_8$Nb, etc). This ordered structure can significantly increase the hardness of the material. For jewelry applications involving Pt and Pd, international hallmarking standards require that the alloys be at least 95\% pure by weight. However, these metals are often soft when purity is high if the minority atoms are disordered. Because the 8:1 structure maintains a high weight percentage of Pt/Pd, it can satisfy purity standards while increasing performance. Recent calculations suggest that the 8:1 structure may form in about 20 previously unsuspected Pt/Pd binary systems. For this study, we investigated the possibility of Pd-rich compounds in Pd-Nb and Pd-Cu.