Thermodynamics, defect structure, and charge transfer in doped lanthanum cobaltites: an overview

This work, based on the experimental and theoretical research performed by the authors during last three decades, presents an overview of phase and defect thermodynamics, electronic transport properties, and the stability of cobaltite-based mixed conductors that are promising for electrode and membrane applications. Attention is centered on (1) the phase equilibria in La-Me-Co-T-O (where Me=Ca, Sr, Ba and T=Mn, Fe, Ni, Cu) systems and crystal structure of the complex oxides formed in these systems, thermodynamic stability and the homogeneity ranges of solid solutions; (2) the defect structure of the oxygen-deficient undoped and acceptor- or/and donor-doped lanthanum cobaltites; and (3) their conductivity and Seebeck coefficient as functions of temperature and oxygen partial pressure. The relationships between the peculiarities of the defect structure and the transport properties of the lanthanum cobaltites with different dopant natures are analyzed.