Morphology and phase modifications of MoO3 obtained by metallo-organic decomposition processes

Molybdenum oxide samples were prepared using different temperatures and atmospheric conditions by metallo-organic decomposition processes and were characterized by XRD, SEM and DRS UV/Vis and Raman spectroscopies. Variation in the synthesis conditions resulted in solids with different morphologies and oxygen vacancy concentrations. Intense characteristic Raman bands of crystalline orthorhombic α-MoO3, occurring at 992 cm−1 and 820 cm−1, are observed and their shifts can be related to the differences in the structure of the solids obtained. The sample obtained under nitrogen flow at 1073 K is a phase mixture of orthorhombic α-MoO3 and monoclinic β-MoO3. The characterization results suggest that the molybdenum oxide samples are non-stoichiometric and are described as MoOx with x < 2.94. Variations in the reaction conditions make it possible to tune the number of oxygen defects and the band gap of the final material.