Description:
<jats:p>The 4:1 cluster model has been considered and its application to the available experimental data for the deviation from stoichiometry, electrical conductivity, and the Seebeck coefticient has been analyzed. It has been shown that the degree of ionization of the cluster is −5. The equilibrium constant of formation is <jats:italic>K</jats:italic><jats:sub>5</jats:sub>= [(<jats:italic>V</jats:italic><jats:sub>Co</jats:sub>)Co<jats:sub><jats:italic>i</jats:italic></jats:sub>]<jats:sup>5−</jats:sup>[h<jats:sup>˙</jats:sup>]<jats:sup>5</jats:sup><jats:italic>p</jats:italic><jats:sub>O2</jats:sub><jats:sup>3/2</jats:sup>= 4.6 exp[−167.5 (kJ)/<jats:italic>RT</jats:italic>]. It has been shown that the applicability of this model in describing CoO properties is limited to higher values of the deviation from the stoichiometric composition (y). At low <jats:italic>y</jats:italic>, defects in CoO can be considered as isolated. Then doubly ionized cobalt vacancies are assumed to be the predominant lattice defects. Their equilibrium constant of formation, determined from experimental data in the vicinity of the Co/CoO phase boundary by using an ideal approximation, is <jats:italic>K</jats:italic><jats:sub><jats:italic>V</jats:italic></jats:sub>= [<jats:italic>V</jats:italic><jats:sup><jats:italic>n</jats:italic></jats:sup><jats:sub>Co</jats:sub>][h<jats:sup>˙</jats:sup>]<jats:sup>2</jats:sup><jats:italic>p</jats:italic><jats:sub>o2</jats:sub><jats:sup>−1/2</jats:sup>= 3.2 × 10<jats:sup>−4</jats:sup> exp[−121.1 (kJ)/<jats:italic>RT</jats:italic>]. Excellent agreement between the equilibrium constant <jats:italic>K</jats:italic><jats:sub><jats:italic>V</jats:italic></jats:sub> determined for low <jats:italic>p</jats:italic><jats:sub><jats:italic>O</jats:italic>2</jats:sub> and that resulting from the Debye Hückel model within the entire range of y has been found.</jats:p>