Oxygen-induced Y surface segregation in a CuPdY ternary alloy

We present a comprehensive theoretical and experimental study of the segregation behavior of the ternary alloy CuPdY in vacuum (i.e., the clean surface) and in the presence of oxygen. Theoretical prediction shows that for clean surface, yttrium will substitute first for Cu and then for Pd at the subsurface lattice site before segregating to the surface where it substitutes for Cu. XRD characterization of the surface of CuPdY indicates the presence of two major phases, B2 CuPd and Pd3Y. In the presence of adsorbed oxygen, theory predicts that Y preferentially occupies surface sites due to its stronger oxygen affinity compared to Cu and Pd. XPS experiments confirm the computational results in the adsorbed oxygen case, showing that surface segregation of yttrium is induced by the formation of Y-oxides at the top-surface of the alloy. ► We study the segregation behavior of CuPdY in vacuum and oxygen rich-environments. ► DFT predicts that Y subsurface segregates in presence of vacuum. ► XRD characterization of CuPdY surface indicates the presence of two major phases. ► In presence of oxygen, Y segregates and forms Y-oxides at the top-surface of CuPdY.