Ab inito thermodynamics: phase stability of perovskite solid solutions

E. Kotomin, M. M. Kuklja*, D. Fuks**, Yu. Mastrikov***

* Materials Science and Engineering, University of Maryland, USA ** Ben Gurion University, Israel ***Institute of Solid State Physics, University of Latvia, Riga

(Ba,Sr)(Co,Fe)O₃ (BSCF) perovskite solid solutions are promising materials for solid oxide fuel cell cathodes and oxygen permeation membranes. Cathode performance could strongly depend on the morphology of these materials remaining a single phase or two-phase mixture. Combining ab initio calculations of the atomic and electronic structure of different supercells with thermodynamics of solid solutions, we have constructed and discussed phase diagrams of several important BSCF chemical compositions. It is demonstrated that in BSC cobaltite solid solution the spinodal decomposition may occur already at relatively low temperatures, while ferrite (BSF and SCF) solid solutions decompose at relatively high temperatures forming a two-phase system where the coexisting hexagonal and cubic phases significantly differ in fractions of constituents.

D. Fuks, Y. Mastrikov, E. Kotomin, and J. Maier Ab initio thermodynamic study of (Ba,Sr)(Co,Fe)O₃ perovskite solid solutions for fuel cell applications Journal of Materials Chemistry A, 1, 14320 (2013). DOI: 10.1039/C3TA12874A  

M. M. Kuklja, Yu. A. Mastrikov, B. Jansang, and E. A. Kotomin First principles calculations of (Ba,Sr)(Co,Fe)O_3-δ structural stability Solid State Ionics 230, 21–26 (2013). DOI: 10.1016/j.ssi.2012.08.022

D. Fuks, A. Weizman, and E. Kotomin Phase competition in (La_1-c,Sr_cCoO₃) solid solutions: ab initio thermodynamic study physica status solidi b 250(4), 864–869 (2013). DOI: 10.1002/pssb.201200851