Co-doped α-MoO3 hierarchical microrods: Synthesis, structure and phonon properties

We present a study on the structural and phonon properties of cobalt-doped orthorhombic molybdenum trioxide (α-MoO3:xCo) hierarchical microrods. The samples were synthesized by solid-state reaction with molar concentrations of 0%, 1%, 3%, and, 5% cobalt. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and Fourier transformed infrared spectroscopy (FTIR) were used to confirm the orthorhombic phase and the structural properties of each sample. The infrared and Raman spectra of the samples show that doping alters the ratio of relative intensities, linewidth, and the shift of the wavenumber of the modes, and a correlation is established between the stretching force constant and wavenumber. Experimental temperature-dependent Raman scattering studies were performed on samples of α-MoO3:xCo over a temperature range of 298–813 K. The Raman spectra showed a phase transition at around 373 K to a self-similar structure, indicating a possible isostructural phase transition (IPT) for samples with 0% and 1% cobalt, a phenomenon rarely reported in the literature. Nevertheless, this phase transition was not observed for samples containing 3% and 5% cobalt, indicating an increase in material stability.