Structural, morphological and optical characteristics of fusiform Co-doped CeO₂ via a facile hydrothermal method

In this study, the fusiform Co-doped CeO₂ particles were prepared by a hydrothermal method and characterized by X-ray diffraction (XRD), thermo-gravimetric differential thermal analysis (TG–DTA), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectrometer (EDX), X-ray photo-electron spectroscopy (XPS), Raman, photoluminescence (PL) and UV–Vis spectroscopy. The cubic fluorite structure of CeO₂ were supported by XRD. Initially thermal gravimetric and differential thermal analysis were used to analyse the reaction mechanism and chemical process, which indicated a crystal temperature of the as-synthesized CeO₂ particles at 600 °C. The reaction concentration of the solution were systematically researched. It is found that the reaction concentration is one key parameter for controlling the final micrographs. The optical properties were characterized by Raman, PL and UV–Vis spectroscopy. It has been demonstrated that oxygen vacancies and Ce³⁺ exist at the particle surfaces and boundaries. The appearance of luminescence peaks and emission peaks can be ascribed to the related oxygen defects. The appearance of Ce³⁺ and oxygen defects existing in fusiform Co-doped CeO₂ products can cause the formation of several local band gap states, which is perhaps responsible for the red shift of band gap.