Ce-Zr-Al-O system with host-guest interactions: Peculiarities of the optical properties

The structural composition and optical properties of glassy Ce-Zr-Al-O samples obtained by a totally inorganic modification of the sol-gel technique were investigated by XRD, FTIR, ESR, UV-Vis, PL and XPS. EPR data indicate the appearance of the Ce3+-defects that are considered as coordinately unsaturated ions in contact with oxygen vacancies-[Ce3+ − VO] (g⊥ = 1.962-1.967, g∥ = 1.938-1.940, assigned to 4f1 state, with concentration ∼2 × 1018 spin/g). The significant PL intensity rising at elevated temperature was related to a spontaneous increase of the Ce3+ concentration in sol-gel samples under thermal dehydration. Also, an unexpected formation of intra-band-gap states during thermal treatment of xero-gels was manifested in UV-Vis and XPS spectra. These intra-band-gap states are attributed to the oxygen-related defects that contribute to the PL signal.