Raman and infrared spectra of doped La8+xSr2−y(SiO4)6O2+δ compounds compared to the ab initio-obtained spectroscopic characteristics of fully stoichiometric La8Sr2(SiO4)6O2

Vibrational spectroscopy data were used to gain insight into the possible locations of extra oxygen ions introduced into La8+xSr2−y(SiO4)6O2+δ compounds to raise their ionic conductivity. Perturbations observed in the Raman and infrared spectra of these compounds with increasing δ were explained by using the ab initio calculation results for the fully stoichiometric (x = y = δ = 0) lattice. This allowed the inference that the extra oxygen ions are incorporated into LaO tunnel‐like fragments inherent in the studied structures. Copyright © 2010 John Wiley & Sons, Ltd. Spectral features in infrared and Raman spectra of La8Sr2(SiO4)6O2 and related oxygen‐excess compounds are discussed on the basis of the results of density functional calculations. Spectral manifestations of oxygen ion modes localized within La‐formed channels are established. They indicate that the excess oxygen ions are localized primarily inside the channels, thus providing valuable information on mechanism of the oxide ion conductivity.