Structure and optical properties of Dy³⁺ activated sol-gel ZnO-TiO₂ nanocomposites

Dysprosium (Dy³⁺) activated ZnO-TiO₂ nanocomposite phosphors were successfully synthesized by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR), UV–Vis spectroscopy, X-ray photoelectron spectroscopy and photo-luminescent (PL) spectroscopy were used to analyze the structure, morphology, chemical and elemental composition, vibrational bending modes and optical properties of the ZnO-TiO₂:Dy³⁺ nanocomposite phosphors. The XRD patterns confirmed crystallization of wurtzite hexagonal ZnO and tetragonal TiO₂ (anatase and rutile) phases. In addition, the XRD patterns showed that secondary phases of ZnTiO₃ and Zn₂TiO₄ were formed. The SEM data showed particle morphology of ZnO-TiO₂ nanocomposites consisted of faceted spheres and hexagons which were shown to vary due to incorporation of Dy³⁺ ions. When excited at 325 nm using monochromatized xenon lamp, the ZnO-TiO₂ nanocomposite phosphor exhibited broad emission in the visible region associated with defects in both ZnO and TiO₂. The proposed reaction mechanism for ZnO-TiO₂ under ultraviolet light irradiation is presented and discussed. The yellowish emission with maximum at ∼587 nm was observed from Dy³⁺ ions when the nanocomposites were excited at 464 nm using the monochromatized xenon lamp in the blue region of the electromagnetic spectrum.