Perovskites: Temperature and Coordination Dependent Ionic Radii

Abstract

Materials LaAlO₃ and A²⁺TiO₃, where A is Ba, Ca, Pb and Sr, have been investigated in order to determine the “effective” temperature dependent ionic radii of 12-fold coordinated Ba²⁺, Ca²⁺, Pb²⁺, Sr²⁺ and La³⁺, and, 6-fold coordinated Al³⁺, Ti⁴⁺ and O²⁻ within the “simple” “ideal” cubic Perovskite structure. The recently developed planar and volume constrained Perovskite model, which incorporates thermal expansion, has been utilized to determine ionic radii values. As compared with Goldschmidt based models, the newly determined radii provide significant improvements for more precise modeling of the lattice parameter of Perovskites at room temperature as well as over extended temperature ranges.

Keywords:

• Temperature dependent ionic radii
• Perovskite
• structural phase transitions
• lattice modeling

Acknowledgments

This material is based upon work supported by, or in part by, the U.S. Army Research Laboratory and the U.S. Army Research Office under contract/grant number W911NF-08-1-0353. The author S.C. Tidrow would like to thank Dr. Art Tauber and Professor Amar Bhalla for many constructive discussions pertaining to development of new Perovskite oxide materials.