Improved photo-luminescence by co-doped lithium in the phosphor system CeO2:Eu3+

Abstract Li + co-doping is used as a prevalent way to improve the luminescent intensity of CeO 2 :Eu 3+ [25]. Here, we investigate the structural and luminescent properties of CeO 2 :Eu 3+ by the different co-doping ways of Li + ions, including the direct co-doping of Li + by hydro-thermal co-precipitation and the indirect co-doping of Li + by a post calcining of Li 2 CO 3 . The different co-doping ways of Li + ions was found to cause different effect on structure and luminescence of CeO 2 :Eu 3+ phosphor. The result showed opposite trend with conventional explanations [25] where the substitution of Ce 4+ with doped Li + ions are the prime reason for luminescence intensity enhancement. Oxygen vacancies should be formed due to the charge imbalance. It is found that the Li + direct co-doped CeO 2 :Eu 3+ didn’t improve the crystallization of the samples due to the increase of oxygen vacancies, as is supported by X-ray diffraction(XRD) patterns and Raman spectra. Meanwhile, the spectroscopic investigations reveal that the Li + direct co-doped CeO 2 :Eu 3+ lead to less asymmetry around Eu 3+ and lower luminescence. However, results show that the indirect co-doping of Li + lead to a increase of crystallinity and decrease in oxygen vacancies concentration. The luminescent intensity of CeO 2 :Eu 3+ can be significantly enhanced by indirect co-doping of Li + . Consequently, we reason that the enhanced luminescence mainly results from a increase of crystallinity and decrease in oxygen vacancies concentration due to the flux effect of Li + ions, instead of the substitution of Ce 4+ with doped Li + ions.