Experimental and Theoretical Characterization of the Optical Properties of CeO₂, SrCeO₃, and Sr₂CeO₄ Containing Ce⁴⁺ (f⁰) Ions

In an effort to find new UV absorbers, the optical properties of CeO 2, SrCeO 3, and Sr 2 CeO 4 were examined by UV−visible diffuse reflectance measurements and electron energy-loss spectroscopy (EELS), and their electronic structures were investigated on the basis of first-principles density functional theory (DFT) calculations. The extinction coefficient k and the refractive index n determined from the loss function Im (−1/ε) by EELS were compared with the corresponding quantities calculated from DFT calculations. The UV absorption thresholds of these materials were determined by the electron excitation from the O 2p anionic band to the empty Ce 4f orbitals. The calculated and measured refractive indices were in satisfactory agreement. The applicability of CeO 2, SrCeO 3, and Sr 2 CeO 4 as potential UV absorbers was assessed.