Grain boundary segregation in yttrium-doped polycrystalline TiO2

Grain boundary segregation of yttrium in titanium dioxide is studied systematically as a function of dopant concentration. Local grain boundary defect chemistry is quantitatively determined by analytical transmission electron microscopy and compared to equilibrium space-charge segregation models that incorporate both the electrostatic and elastic strain-energy driving forces for solute segregation. The thermodynamic models show that the elastic strain-energy driving force dominates in this system and that the electrostatic driving force contributes a 10-20% correction to the total solute segregation. In comparison to the experimental results, the theoretical models provide good predictions for several grain boundary parameters including local stoichiometry, solute interfacial excess and space-charge layer thickness. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.