On the solubility of yttrium in RuO2

We have investigated the solubility of Y in rutile RuO(2) using experimental and theoretical methods. Nanostructured Ru-Y-O thin films were synthesized via combinatorial reactive sputtering with an O/metal ratio of 2.6 and a Y content of 0.3 to 12.6 at. %. A solubility limit of 1.7 at. % was identified using x-ray photoelectron spectroscopy and x-ray diffraction. Based on ab initio and thermodynamic modeling, the solubility of Y can be understood. Smaller Y amounts are incorporated into the lattice, forming a metastable film, with local structural deformations due to size effects. As the Y content is increased, extensive local structural deformations are observed, but phase separation does not occur due to kinetic limitations. Nanostructured RuO(2) alloyed with Y might lead to enhanced phonon scattering and quantum confinement effects, which in turn improve the thermoelectric efficiency. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633234]