Comparative study of the conductivity of synthesized bivalent vanadates CaV₂O₆ and MnV₂O₆

We have studied the layered compounds of polycrystalline vanadates CaV₂O₆ and MnV₂O₆, synthesized by a conventional solid-state reaction technique, because of their interesting applications such as optoelectronic materials, dielectric ceramics, semiconductors, magnetic candidates, catalytic materials, etc. The crystal phase and structures were analyzed by X-ray powder diffraction (XRD). The detailed surface morphologies were characterized by scanning electron microscopy (SEM). The temperature dependence of electrical resistivity of these vanadates shows semiconducting nature, which is consistent with their electronic band structures studied by first principles density functional theory (DFT). The energy band gap of CaV₂O₆ is larger than that of MnV₂O₆. The dominant contribution to the bottom of the conduction band in the total density of states (TDOS) mainly comes from the V 3d electrons in both vanadates. Indeed, the Fermi level lies in the conduction band rather than in the forbidden region in MnV₂O₆ indicating the degeneracy of metavanadates. Using Wood–Tauc theory, the calculated optical band gap from the observed absorbance by a UV–Visible spectrophotometer is almost similar with their electronic band gap.