An atomistic simulation study was made of the incorporation of ions of the first series of transition metals (Cr3+, Cr4+, Fe2+, Fe3+, Co2+, Co3+, Ni2+, Ni3+), Y3+ and ions of the lanthanide series (Er3+, Gd3+, Tb3+, Pr3+, Pr4+, La3+) into BaTiO3. It was found that ions of the transition metals preferred to substitute at the Ti site, with O-vacancy compensation. For Fe and Co, oxidation from the divalent to the trivalent state during incorporation was favored. The Ni and Cr were preferentially incorporated with the valences 2+ and 3+, respectively. The formation of stable defect pairs with various types of lattice defects was predicted for the transition-metal impurities. In the case of La3+ and Pr3+, substitution occurred at the Ba site, whereas Y3+, Tb3+, Gd3+ and Er3+ tended to substitute simultaneously at both cation sites. The formation of dopant-Ti-vacancy pairs was predicted for the rare-earth ions, and Y3+. The effect of doping upon the lattice parameter was studied by means of mean-field calculations. A comparison with experimental data confirmed the dependence of the preferred substitution site upon the ionic radius of the impurity. In the case of dopants of intermediate size (Y3+, Er3+, Tb3+, Gd3+), the Ba/Ti ratio was important in determining the incorporation mechanism.

Atomistic Simulation of Dopant Incorporation in Barium Titanate. M.T.Buscaglia, V.Buscaglia, M.Viviani, P.Nanni: Journal of the American Ceramic Society, 2001, 84[2], 376-84