First principles studies of SnTiO3 perovskite as a potential ferroelectric material.
Résumé
In the context of the search for environment-respectful, Pb- and Bi- free chem. compds. for devices such as actuators, SnTiO3 (ST) is investigated from first principles within DFT. Full geometry optimization provides a stable tetragonal structure relative to cubic one. From the equation of state the equil. vol. of SnTiO3 is found smaller than ferroelec. PbTiO3 (PT) in agreement with a smaller Sn2+ radius. While ionic displacements exhibit similar trends between ST and PT a larger tetragonality (c/a ratio) for ST results in a larger polarization, PST = 1.1 C.m-2. The anal. of the electronic band structure detailing the Sn-O and Ti-O interactions points to a differentiated chem. bonding and a reinforcement of the covalent bonding with respect to Pb homolog