Investigations of the Morphology and Optical Properties of Cadmium Tungstate Nanostructures

Abstract

Nanocrystalline CdWO₄ particles were synthesized via a co-precipitation method using diethylene glycol (DEG) as a capping agent, followed by a hydrothermal technique. Synthesized samples were characterized via X-ray diff raction (XRD), scanning electron microscopy (SEM), dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy, and UV-visible absorption and photoluminescence analysis. XRD analysis confi rmed the formation of a monoclinic structure in CdWO₄. Uniform homogeneous NanoRect long rod-like morphologies with lengths of <20 to 300 nm were observed via SEM. Hydrodynamic size distribution of the synthesized particles increased with increasing DEG concentration from 20 to 1500 nm. Raman analysis confi rmed the monoclinic structure of the prepared CdWO₄. The width of the strong vibration mode at 897 cm^–1 decreases as the annealing temperature increases, indicating that the crystallite size increases as the crystal evolves with temperature. The band gap of CdWO₄ was found to vary between 2.47 and 4.06 eV from the UV-Vis absorption measurements. Bandgap increases with increasing lattice strain, which is refl ected by the calculated XRD results. UV-visible measurements reveal that the bandgap of CdWO₄ increases with strain in the sample. A broad intense emission peak was observed at 482 nm when the samples were excited at 298 nm.