Electronic Structure and Ferroelectric Behavior of Lanthanum Substituted Bismuth Titanate

The effect of substituting La for Bi atoms in Bi ₄ Ti ₃ O ₁₂ is investigated from first-principles calculations using the full-potential linearized augmented plane wave (LAPW) method. A comparative study of the electronic structure and lattice-dynamics properties of Bi ₄ Ti ₃ O ₁₂ and La ₂ Bi ₂ Ti ₃ O ₁₂ shows the role of covalent bonding in the ferroelectric instabilities. The displacement patterns displayed by unstable zone-center phonon modes and a detailed analysis of the orbital contribution to the valence band illustrate the importance of Bi (La)-O interactions for the ferroelectric behavior of the doped material.

Keywords:

• Aurivillius
• BIT
• first-principles

Acknowledgments

This work was supported by Agencia Nacional de Promoción Científica y Tecnológica and Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina). R.M. thanks Fundación Josefina Pratts. M.G.S. thanks support from CIUNR.

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005;