The thermodynamic parameters of oxygen nonstoichiometry defects in lanthanum cobaltite doped with acceptor impurities (Sr and Ni)

The oxygen nonstoichiometry delta of landthanum cobalite doped with acceptor impurities (Sr and Ni), La1-xSrxCo0.9Ni0.1O3-delta (x = 0.1, 0.3), was studied by high-temperature thermoggravimetry over the temperature and pressures ranges 723 K <= T <= 1373 K and 10(-3) atm <= P-O2 <= 1 atm. The partial replacement of cobalt with nickel and lanthanum with strontium increased the oxygen nonstoichiometry delta. The partial molar enthalpies Delta(H) over bar (O)degrees and entropies Delta(S) over bar (O)degrees of solution of oxygen in the solid phase were calculated. Models of point defect formation were suggested and analyzed. The equilibrium constants of formation and concentrations of predominant point defects, ionized oxygen vacancies V-O(++), holes Me-Co(+) (Co-Co(+) and Ni-Co(+)), and electrons Me-Co(+) (Co-Co(+) and Ni-Co(+)) localized on 3d transition metals, were determined by nonlinear regression from the experimental and theoretical logp(O2)-delta dependencies.