ON THE SUBSTITUTION SITE OF CR AND FE IN LINBO3 - AN EXAFS STUDY

K-edge EXAFS spectra of 5 molar% Cr or Fe have been observed in LiNbO3 and also in Mg co-doped samples. The results in congruent LiNbO3 can be interpreted in terms of a relaxed Li substitution model, however, i n the case of Cr, the formation of pairs occupying Li and Nb sites see ms also to be important. In stoichiometric or Mg-containing samples Fe is partly displaced to the Nb site while for Cr the dominating proces s seems to be the formation of aggregates with the participation of Mg .