Investigation on the Thermal Decomposition Behavior of Molybdenum Trioxide Precursor

The ultrafine MoO3 powders were prepared by the combination of centrifugal spray drying and calcination in this work. The thermal decomposition behavior of the spherical precursor was studied. The phase constituents, morphologies, particle size, and specific surface areas of MoO3 powders were characterized at different temperatures. It is found that the decomposition of the precursor is subjected to five stages, and forms different intermediate products, including (NH4)8Mo10O34, (NH4)2Mo3O10, (NH4)2Mo4O13, h-MoO3, and the final product α-MoO3. Moreover, the decomposition rate equation is established based on the thermal decomposition kinetic parameters of the precursor. With an increase in decomposition temperature, the morphology changes from unclear boundary particles to dispersed flake particles, and the flaky particles exhibit larger sizes, higher crystallinity, and better dispersion, which can be attributed to the mass transfer of gaseous MoO3 products. Additionally, the MoO3 particle size decreases progressively, and the specific surface area increases and then decreases. At 500 °C, it can achieve ultrafine flaky MoO3 powder with the size of thick sheets, with a thickness of about 300 nm and a length of about 1–3 μm. This research can offer an innovative strategy for preparing ultrafine MoO3 powder.