First-Principles Calculations of Rare-Earth Dopants in BaTiO3

Rare-earth dopants, particularly Dy and Ho, are considered to play an important role in determining the reliability of dielectrics used in multi-layer ceramic capacitors (MLCCs). However, a detailed examination of the solution energies and compensation mechanisms of these elements has not been reported. In this paper, quantitative analysis of the substitution of rare-earth elements La, Dy, and Ho in perovskite-type BaTiO3 using first-principles calculations in combination with chemical thermodynamics is reported. The solution energies of vacancy, n-type, and p-type compensated dopants have been systematically calculated. Substitution onto the two crystallographically different cation sites in cubic BaTiO3 under four different thermodynamical conditions with different chemical potentials is also examined. Dy and Ho are both found to be stable on both Ba and Ti sites, depending on the thermodynamical conditions. In contrast, La preferably occupies the Ba site under all the conditions examined. These results agree well with experimentally determined site preferences. Our calculations reveal features common to both Dy and Ho incorporation in BaTiO3. (C) 2009 The Japan Society of Applied Physics