Point defect diagrams for pure and doped cobalt oxide $$ {\hbox{C}}{{\hbox{o}}_{{{1} - }}}_{\delta }{\hbox{O}} $$ in the temperature range of 1,173–1,673 K (I)

Abstract

The point defect diagram in non-stoichiometric cobalt oxide Co 1Àd O, pure and doped with M 3+ and M + metal ions, taking into consideration all of the types of defects in the cation sublattice are presented in this work. A new method was used for the calculations of the diagrams. This method is based on the derived relations between the standard Gibbs energies of formation of cobalt vacancies and the intrinsic ionic and electronic defects; it also uses the experimental values of the deviation from the stoichiometry. The calculations were performed using the results of studies obtained by many authors in the temperature range of 1,173-1,673 K.

Defect Complexes and Defect Clusters in Mn1-deltaO, Co1-deltaO and Ni1-deltaO Oxides Diagrams of the Concentrations of Point Defects

“…The work (Stokłosa, 2011a) also demonstrated that the standard Gibbs energy of the formation of vacancies…”

“…Due to a low concentration of defects, the concentrations of defect complexes and defect clusters will also be low. It could be demonstrated very clearly that near the stoichiometric composition (δ0) the changes of the concentrations of the defects are infinitesimally small, yet are of the same order of magnitude (Stokłosa, 2011a). This is why the changes of the concentrations of defects (mole fractions) in Eqs.…”

“…In the previous work (Stokłosa, 2011a) the calculations of diagrams of point defects in Co 1-δ O were presented, assuming in the first approximation the presence of cobalt vacancies and interstitial ions with the highest ionization degree and lower ionization degrees. The obtained character of the dependence of …”

“…This is why the changes of the concentrations of defects (mole fractions) in Eqs. (A13) -(A15) and (A35) will tend to the values occurring at the stoichiometric composition (Stokłosa, 2011a). As such, if we assume that near the stoichiometric composition the concentration of complexes can be neglected, then the assumed approximation and the compensation of the concentrations of defects cause that the Eq.…”

“…In the previous works (Stokłosa, 2011a(Stokłosa, , 2011b(Stokłosa, , 2012, the calculations of the diagrams of the concentrations of point defects were performed, for Co 1-δ O, Ni 1-δ O and Mn 1-δ O, using the results of the studies of the deviation from the stoichiometry by different authors, assuming as a first approximation that there are cation vacancies and interstitial metal ions with different ionization degrees. A new method was used there for the calculations of the diagrams.…”