Macrosegregation of alumina in LiNbO3 single crystals

The macrosegregation of Al impurities has been studied in Czochralski grown LiNbO3 single crystals. Macrosegregation profiles determined by neutron activation analysis are presented and compared to predictions to the solutions of the neglect of parallel motion (NPM) model. A brief description of this model is given and a new formula is suggested for the interface segregation coefficient, k*, which accounts for different mechanisms of impurity incorporation due to the onset of criticalities. Optimization of model parameters led to fairly good agreement between observed and calculated profiles. Thus we have been able to give an upper estimate for the equilibrium distribution coefficient (k0) of Al. A numerical procedure was developed to assess the errors of the optimized model parameters. (author)