Structural, morphological and optical properties of shuttle-like CeO2 synthesized by a facile hydrothermal method

In this study, the shuttle-like CeO2 particles were synthesized by hydrothermal method and characterized by X-ray diffraction (XRD), TG, scanning electron microscopy (SEM), Photoluminescence (PL), UV-vis and Raman analyses. The cubic fluorite structure and average particle size of ceria were confirmed by XRD. Initially differential thermal analysis and thermal gravimetric were used to analyze the reaction process and chemical mechanism, which suggested a crystallization temperature of the as-synthesized CeO2 powder at 600 degrees C. The reaction time and the reaction concentration of the solution were systematically investigated. It is found that the reaction time and the reaction concentration are key parameters for controlling the final morphology. Mixed oxidation states (Ce4+ and Ce3+) were detected in the samples, confirmed using X-ray photo-electron spectroscopy (XPS) and Raman. It has been proven that oxygen vacancies and Ce3+ ions exist at the grain surface and at the grain boundaries. The appearance of emission peaks and the visible luminescence peaks can be attributed to the oxygen related defects. The existence of Ce3+ ions and oxygen defects existing in shuttle-like CeO2 samples can lead to the formation of some localized band gap states, which is possibly responsible for the red shifting of band gap. (C) 2017 Elsevier B.V. All rights reserved.