Molybdenum–Ruthenium–Carbon Solid-Solution Alloy Nanoparticles: Can They Be Pseudo-Technetium Carbide?

Technetium (Tc), atomic number 43, is an element that humans cannot freely use even in the 21st century because Tc is radioactive and has no stable isotope. In this report, we present molybdenum–ruthenium–carbon solid-solution alloy (Mo_xRu_1–xC_y) nanoparticles (NPs) that are expected to have an electronic structure similar to that of technetium carbide (TcC_y). Mo_xRu_1–xC_y NPs were synthesized by annealing under a helium/hydrogen atmosphere following thermal decomposition of metal precursors. The obtained NPs had a solid-solution structure in the whole composition range. Mo_xRu_1–xC_y with a cubic structure (down to 30 atom % Mo in the metal ratio) showed a superconducting state, and the transition temperature (T_c) increased with increasing Mo composition. The continuous change in T_c across that of TcC_y indicates the continuous control of the electronic structure by solid-solution alloying, leading to pseudo-TcC_y. Density functional theory calculations indicated that the synthesized Mo_0.53Ru_0.47C_0.41 has a similar electronic structure to TcC_0.41.