Controlled synthesis of monodispersed spherical ruthenium powders

Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets, which have applications in very-large-scale integration circuits and magnetic recording devices. However, the synthesis of such powders remains a major challenge. Here, we reported the synthesis of monodispersed spherical Ru powders through controlling the molar ratio of SO 4 2− to Ru 3+ in urea homogeneous precipitation solution and the annealing conditions. Without the addition of (NH 4 ) 2 SO 4 into the reaction solution, only gel-like precipitation particles were obtained. Once introducing (NH 4 ) 2 SO 4 into the reaction solution and controlling the molar ratio of SO 4 2− to Ru 3+ between 0.50 and 1.00, monodispersed spherical precursor powders were obtained. The nucleation and growth of monodispersed spherical precursor particles in solution were found to conform to LaMer’s model. Through controlled annealing at 450 °C in a hydrogen atmosphere, the obtained metallic Ru powder with an average particle size of 135 nm inherited the spherical morphology and excellent dispersity from the monodispersed spherical precursor powders. These results and findings would deepen the understanding of the preparation of monodispersed Ru and Ru-like powders. Graphical abstract