Microstructure profiling, lattice dynamics, and morphological studies on multi-excitonic vanadium bismuth oxide compound systems

The solubility limit of bismuth in orthorhombic structured vanadium pentoxide is determined in V_2-xBi_2xO_5-δ compound systems. Highly polycrystalline single-phased solid solutions of V_2-xBi_2xO_5-δ were synthesized for mole fractions “x” varying from 0.01 to 0.04 and at x = 0.05, the compound contorts into an impure phase. Orthorhombic structured compounds with crystallite sizes varied from 54.80 to 70.23 nm are observed from powder X-ray diffraction analysis and supplementary structural information was obtained by recording micro-Raman spectra. Out of the 21 Raman active phonon modes of the α-polymorphic form of V₂O₅, 10 well-resolved peaks were identified for all “x” values. The dense growths of microstructured constituents were obtained, viz. scanning electron micrographs. The slight increase of optical bandgap from 2.22 to 2.27 eV with the increase in mole fraction is an indication of the replacement of high valency vanadyl cations with Bi³⁺ ions. Intense and broad near-band edge photoluminescent emissions detected are due to the various electronic transitions.