Photoluminescence Properties of CeO₂:Eu³⁺ Nanoparticles Synthesized by a Sol-Gel Method

Abstract

Nanocrystalline Eu3+-doped CeO2, CeO2, Sm3+-doped CeO2, and Li+, Eu3+-codoped CeO2 samples were prepared through a sol−gel process. The structure and the optical properties of the samples were characterized by X-ray diffraction, diffuse reflection spectra, and photoluminescence spectra. No luminescence was observed for nanocrystalline CeO2. The systematic investigation shows that the broad band in the excitation spectrum of CeO2:Eu3+ comes from the charge transfer (CT) transition from O2− to Ce4+, not from the oxygen vacancy, or from the CT of O2− to Eu3+. Upon increasing the fired temperature from 600 to 800 °C, the excitation spectrum shifts to lower energy. With increasing concentrations of Eu3+ up to 1% in CeO2, red shifts of the excitation spectra are observed; however, when the concentration of Eu3+ increases to 5% and 10%, blue shifts occur. The emission spectrum shows that the symmetry of the Eu3+ site becomes lower with increasing Eu3+. Based on the dielectric theory of complex crystals, the environmental factor (h e) and the dielectric definition of average energy gap around the centers of Eu3+ are calculated. The reasons for the shifts of the excitation spectra are discussed in detail.

Optical and structural properties of nanostructured CeO2:Tb3+ film

“…Recently, luminescent metal ions doped cerium oxide nanophosphors with a narrow size distribution (<10 nm) and high luminescent efficiencies are of great importance because of their applications in high-performance luminescent devices, biological fluorescence labeling, luminescent paints and inks for security codes [1][2][3][4]. Because, these metal oxide nanophosphors possess higher chemical and thermal stability than commonly used mixed metal alloy phosphors such as ZnS:Cu, Al and Y 2 O 2 S:Eu 3+ [5,6].…”

“…Generally rare earth (RE) ions based on intra-configurational electronic transitions show sharp spectral transitions in visible region arising from their 4f electrons [1,7,8]. When combined with ultra-violate light emitting diode (UVLEDs), phosphors should be in a thin-film form and provide advantages such as high emission efficiencies, good compatibility with semiconductor devices and low fabrication cost.…”

“…be a promising photoluminescence host material because of strong light absorption through the charge transfer (CT) from O 2− to Ce 4+ [1][2][3][4][5][6][7][8].…”

Effects of Li+ Codoping on the Optical Properties of SrAl2O4 Long Afterglow Ceramic Phosphors

“…The addition of Li + probably increases the number of oxygen vacancies, which might act as a sensitizer for the energy transfer to rare-earth ions due to the strong mixing of charge transfer states resulting in the highly enhanced emission intensity [10]. However, the phosphorescence quenching also occurs at higher doping content of Li + due to the excess oxygen vacancies at the host, which destroy the crystallinity of the host material [11].…”

Local structure in CeO2 and CeO2–ZrO2 nanoparticles probed by Eu luminescence

“…As observed from the literature, the emission spectra of Eu doped CeO 2 nanoparticles (NPs) is more complex, besides the cubic type emission, a non-negligible contribution from the forbidden electric dipole emission ( 5 D 0 -7 F 2 ) around 600-640 nm is also measured. These observations converge to the existence of one or more of so-called perturbed or asymmetric Eu centers besides that of cubic center [11][12][13]. Nonetheless, the number of these perturbed sites/centers and their correlation with the chargecompensation defects induced by trivalent doping in CeO 2 are still not elucidated.…”