STUDY OF SC2O3-DOPED CERIA BY ANELASTIC RELAXATION

Anelastic relaxation experiments on Sc**3** plus -doped ceria were undertaken in order to better understand the origin of the very high Sc-V//0 association energy obtained from conductivity data (where V//0 plus or minus oxygen vacancy). Instead of a simple anelastic peak due to the relaxation of pairs, as found for Y**3** plus -doped ceria, a broad peak (made up of at least 2 Debye peaks) was found in the range of activation enthalpy H//r equals 0. 45 to 0. 54 ev. Unexpectedly, an additional small peak was observed at lower temperatures, for which H//r equals 0. 21 ev. The dependence of this peak on double doping (i. e. with both Sc**3** plus and Y**3** plus ) suggests that it is due to Sc//C//e defects, which would have to go off-center in order to account for the relaxation. Computer simulation calculations have demonstrated a modified off-center behavior in which nn O**2** minus ions are displaced asymmetrically to a stable dipolar configuration.