Doping Behavior of Zr⁴⁺ Ions in Zr⁴⁺-Doped TiO₂ Nanoparticles

Abstract

TiO₂ nanoparticles doped with different concentrations of Zr⁴⁺ ions were prepared by the sol–gel method and annealed at different temperatures. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HRTEM) techniques were used to investigate the existing states and doping mechanism of dopants as well as the phase transition of the Zr⁴⁺-doped TiO₂ samples. It was revealed that the doping behavior of introduced Zr⁴⁺ ions was closely related to the doping concentration. The Zr⁴⁺ ions would replace the lattice Ti⁴⁺ ions directly in substitutional mode at a certain annealing temperature. Moreover, if the concentration of doped Zr⁴⁺ ions is high enough, excess Zr⁴⁺ ions would form ZrTiO₄ on the surface of TiO₂. In addition, the phase transition temperature from anatase to rutile increases significantly after doping Zr⁴⁺ ions, due to their larger electropositivity and radius than those of Ti⁴⁺ ions. Our results may afford a better understanding on the doping mechanism and aid in the preparation of Zr-doped TiO₂ with high photoelectric performance