Effect of Calcination Temperature on the Structural, Thermodynamic, and Optical Properties of MoO3 Nanoparticles

Temperature dependence of the structural, thermodynamic, and optical properties of MoO3 nanoparticles synthesized using sol-gel and sonication methods were studied. MoO3 nanoparticles showed variation in crystallite shape from hexagonal to orthorhombic and crystallite size in the range 3.05-5.21nm with bandgap in the range 4.11-4.36eV with change in the calcination temperature and the method of synthesis. Rietveld refinement of the X-ray diffraction (XRD) data confirmed the crystallite phase transition with space group PE and Pbnm with change in the lattice parameter ratio. Activation energy was calculated using XRD and TGA-DSC (thermogravimetry-differential thermal analysis) data and was found to be close to 4kJ/mol. The bandgap fluctuation was due to the size dependence of the blue shift, which indicates strong quantum confinement due to the Bohr radius effect. Optical parameters such as the extinction coefficient, refractive index, optical conductivity, dielectric functions, and Urbach energy were calculated and found to depend on electron-phonon interactions.