Phase evolution of hydrothermal synthesis oxide-doped molybdenum powders

Abstract MoO3 and oxide-doped molybdenum powders have been recently attracted considerable attention due to their superior sensing and photocatalysis properties and great lubricity. In the present study, we report synthesis powders of Mo doped with Al2O3, ZrO2 or La2O3 oxides, respectively, via calcination and hydrogen reduction of uniform and well-crystallized MoO3·(H2O)0.333 nanosheets synthesized by a facile hydrothermal synthesis method. Results show the MoO3·(H2O)0.333 was transformed to h-MoO3, β-MoO3, α-MoO3, MoO2 and Mo in sequence in calcining and reduction process. The three kinds of oxides have a similar effect on the powders in inhibiting grain growth to promote grain refinement at each stage, but they have different effect on growth morphology of Mo particles. The metal oxides (Al2O3, ZrO2) do not affect the morphology of Mo particles, and Mo particles grow into microsphere spontaneously. Nevertheless, the rare earth oxide La2O3 with higher surface activity changes the coordination environment of Mo O bonds and growth process of Mo particle, resulting in a polygonal shape of Mo particles. The Mo powders doped with 1.2 vol%Al2O3 have a fine size of 2 μm, regular morphology and good distribution.