Fast and continuous obtaining of Eu3+ doped CeO2 microspheres by ultrasonic spray pyrolysis: characterization and photocatalytic activity

Abstract

In this work, CeO2:xEu3+ (x = 0, 0.01, 0.02, 0.04 and 0.08 mol%) microspheres were obtained by the fast and continuous ultrasonic spray pyrolysis method. Powders were characterized by X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), scanning electronic microscopy (FESEM), Raman spectra, UV–Visible spectroscopy (UV–Vis) and photocatalytic activity. All XRD patterns were indexed by the cubic structure of the fluorite type, without the presence of secondary phases, indicating success in the Eu3+ doping in the CeO2 structure. In addition, The XRF analysis confirmed the presence of Eu in the CeO2 powders. In the Raman spectra of the samples occurs the vibrational mode F2g, which is a characteristic band of materials with the fluorite type structure. Moreover, as the Eu3+ ion increased, it was noticed the appearance of additional bands referring to oxygen vacancies. FESEM showed that the CeO2:xEu3+ particles have a spherical morphology with homogeneous chemical composition and particle size between 73 and 1560 nm. It can be seen a slight increase of defects in their morphology as the Eu3+ ion increases. The band gap varies between 3.22 and 3.28 eV, being influenced by defects in oxygen vacancies and the concentration of Ce3+ ion. The addition of Eu3+ generates the introduction of intermediary levels in the conduction band of CeO2, besides increasing the reactive species effects, favoring the photocatalysis of Rhodamine B dye.