Laser-Excited Luminescence of Trivalent Lanthanide Impurities and Local Structure in CeO₂−ZrO₂ Mixed Oxides

In this paper we report on the laser-excited Raman and luminescence spectroscopy of a series of ceria−zirconia mixed oxides, containing trivalent lanthanide ions as unintentional impurities, using 488.0-, 514.5-, and 1064.0-nm excitation wavelengths. We assigned the main bands located at Stokes shifts higher than 800 cm - 1 from the laser lines to f−f emission transitions of Pr 3+, Nd 3+, Ho 3+, and Er 3+ ions. These ions can also be used as spectral probes of the cation sites in the solid solutions as their transition intensities are found to be dependent on the local symmetry of the sites in which they are accommodated. f−f emission transitions have also been found to overlap the vibrational Raman bands for Stokes shifts lower than 800 cm - 1 from the laser lines. To overcome possible ambiguities in the structural information extracted from the Raman spectra, at least two laser excitation lines must be used.