Doping Behavior of Zr⁴⁺Ions in Zr⁴⁺-Doped TiO₂Nanoparticles

TiO 2 nanoparticles doped with different concentrations of Zr 4+ 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 Zr 4+ -doped TiO 2 samples. It was revealed that the doping behavior of introduced Zr 4+ ions was closely related to the doping concentration. The Zr 4+ ions would replace the lattice Ti 4+ ions directly in substitutional mode at a certain annealing temperature. Moreover, if the concentration of doped Zr 4+ ions is high enough, excess Zr 4+ ions would form ZrTiO 4 on the surface of TiO 2 . In addition, the phase transition temperature from anatase to rutile increases significantly after doping Zr 4+ ions, due to their larger electropositivity and radius than those of Ti 4+ ions. Our results may afford a better understanding on the doping mechanism and aid in the preparation of Zr-doped TiO 2 with high photoelectric performance.