Ab Initio and Experimental Raman Study of Rare-Earth Oxide Phases in (Y0.2Eu0.2Gd0.2La0.2Er0.2)2O3 High-Entropy Ceramics

The vibrational properties and crystal structures of rare-earth oxides, specifically yttrium (Y2O3) and lanthanum (La2O3) ones, were investigated using a combination of density functional theory (DFT) calculations and experimental Raman spectroscopy. Simulated Raman scattering spectra for the reference oxides enabled the identification of vibrational mode symmetries for each phase. By correlating the measured spectra of high-entropy (Y0.2Eu0.2Gd0.2La0.2Er0.2)2O3 ceramics with DFT results, the crystal structure of the material was determined, and the symmetries of its vibrational modes were assigned. Comparative analysis revealed the presence of the principal La2O3 vibrational mode of Eg symmetry at 365 cm–1 in the high-entropy ceramics. DFT-based modeling provides a useful tool for probing the optical characteristics of rare-earth oxides and can support structural and vibrational characterization. The calculated Raman spectra showed good agreement with both existing theoretical data and experimental results within the acceptable calculation error. This result confirms the applicability of DFT-based modeling for probing the optical characteristics of high-entropy materials, and rare-earth oxide ceramics.