Scandium Molybdate Microstructures with Tunable Phase and Morphology: Microwave Synthesis, Theoretical Calculations,...

In this paper, scandium molybdate microstructures have been prepared from solution via a microwave heating method. By controlling the experimental parameters such as molar ratio of reagent and reaction time, scandium molybdates with tunable phase and diverse morphologies including snowflakes, microflowers, microsheets, and branched spindles were obtained. The density of states and surface energies of Sc₂Mo₃O₁₂ were primarily studied from first-principles calculations. An indirect band gap of 3.56 eV was observed for crystalline Sc₂Mo₃O₁₂, and the surface energies of various facets were determined to be 0.27-0.91 J/m². The influence of n(Sc³⁺): n(Mo₇O₂₄^6-) (short for Sc/Mo) molar ratio was systematically investigated and well-characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and UV-vis absorption spectroscopy (UV-vis). Results indicate that the Sc/Mo molar ratio has a great effect on the phase and morphology. Diffuse reflection spectra (DRS) revealed the E_gap can be readily tuned from 3.69 to 4.16 eV, which is in accordance with the theoretical result. The photoluminescence (PL) properties of Eu³⁺-doped Sc₂Mo₃O₁₂ were discussed. This facile synthesis strategy could be extended to the synthesis of other molybdates.