Influence of local structure on photoluminescence properties of Eu3+ doped CeO2 red phosphors through induced oxygen vacancies by contrasting rare earth substitutions

A new family of red phosphors, Ce0.9-xRExO2-delta:0.1Eu(3+) (RE = Y and La; x = 0, 0.20, 0.40, 0.60, 0.80, and 0.90), was synthesized by a conventional solid-state route. The influence of contrasting rare earth substitutions (Y and La) in the system was investigated on the local structure and associated photoluminescence properties by various characterization techniques. Both trivalent ion substitutions lead to the same kind of variation during phase transformation from fluorite to the respective parent oxide structure (x >= 0.6). On the other hand, the substitutions have a distinct effect on local structure, absorption, luminescence and lifetimes. The smaller Y3+ ion substitution enables the ordering of oxygen vacancies in a lattice, inhibiting the defect formation of Ce3+ oxidation states. In contrast, the larger La3+ ion substitution liberates oxygen vacancies, allowing defect formation. Consequently, the concentration of Ce3+ is dependent on the ionic radius of the metal ions and it has a bearing on the band gap and luminescence properties of the system. Ce0.1Y0.8O2-delta:0.1Eu(3+) phosphor exhibited maximum red emission intensity at 612 nm, which is 8 times higher than that of Ce0.9O2-delta:0.1Eu(3+) and better than that of commercial Philips red phosphor, whereas La substitution yielded poor emission intensities with higher concentrations. The co-substitution of contrasting rare earth metals with Eu3+ allow the understanding of local structure and a smaller ion like Y3+ greatly functionalizes CeO2:Eu3+ phosphor.