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The disordered LaBaCoO ↔ ordered LaBaCoO transition was studied in detail using several complementary in situ (X-ray diffraction, thermogravimetry, and coulometric titration) and ex situ (transmission electron microscopy) techniques. This transition was found to proceed through the formation of complex domain textured intermediate products. They were shown to have strong affinity to oxygen and exhibit its fast absorption from ambient atmosphere (oxygen partial pressure ( pO) 0.21 atm) at a temperature as low as 70 °C. The thermodynamic stability limits of the cubic and double perovskites were determined by coulometric titration. The stability diagram of the LaBaCoO - LaBaCoO system was plotted as a result. Oxygen nonstoichiometry of the thermodynamically stable cubic perovskite LaBaCoO was measured as a function of pO in the temperature range between 1000 and 1100 °C using a coulometric titration technique.

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Perovskite-type complex oxide La0.5Ba0.5CoO3–δ, promising cathode material for solid oxide fuel cells and precursor for synthesis of double perovskite LaBaCo2O6–δ, was prepared as a single-phase material. Its oxygen content was measured by two independent techniques in the temperature range 1000–1100 °C and at oxygen partial pressures corresponding to the stability field of cubic phase. The defect chemistry of this material was studied using the measured δ=f(pO2,T) dependences. The defect structure model based on the localized nature of the electronic defects was proposed and successfully verified.

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