Spectroscopic insights into structural and electronic modifications in Ce0.8Zr0.2O2 under low-energy ion irradiation

This study presents a comprehensive spectroscopic investigation of defect formation and structural stability in polycrystalline Ce0.8Zr0.2O2 subjected to 1.75 MeV Xe5+ ion irradiation up to a fluence of 1 × 1017 ions/cm2. Building on our earlier structural analysis of Xe-induced defects in Ce0.8Zr0.2O2, we employ Raman spectroscopy, synchrotron-based x-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), and photoluminescence (PL) to elucidate atomic-scale structural and electronic modifications. Raman analysis reveals the emergence of Ce3+ and oxygen-vacancy-induced distortions, evident from peak broadening and shifts associated with B1g, F2g, and LO phonon modes. The extent of structural disorder is quantified from Raman intensity ratios and FWHM broadening, revealing damage region diameters of ∼0.31 ± 0.03 and ∼0.22 ± 0.03 nm, respectively. XPS confirms the partial reduction of Ce4+ to Ce3+ and Zr4+ to Zr3+, along with oxygen-vacancy formation that contributes to lattice relaxation and stabilization of the fluorite structure. UV–Vis DRS measurements show a decrease in optical bandgap from 3.37 to 2.71 eV and an increase in Urbach energy from 1.09 to 2.33 eV, indicating enhanced electronic disorder. PL intensity is quenched upon irradiation due to increased non-radiative recombination through defect centers. These findings provide a coherent spectroscopic framework to understand irradiation-driven redox and defect processes in Ce0.8Zr0.2O2. Its retained crystallinity while accommodating high defect densities highlights its promise as a radiation-tolerant matrix for advanced nuclear and extreme-environment applications.