Bi-doped lanthanum manganite La1 - xBixMnO3 + y (x = 0-1) (LBM) and fluorite-like Bi1.5Y0.3Sm0.2O2 oxide (BYS) were synthesized via Pechini route and characterized by a complex of physical-chemical methods. Oxides with reasonable high lattice oxygen mobility and reactivity were selected for LBM + BYS nanocomposites preparation. LBM + BYS composites were prepared via ultrasonic dispersion of the mixture of perovskite and fluorite powders in isopropanol with addition of polyvinyl butyral. Studies of the real structure evolution of composites at sintering under air up to 850 degrees C revealed some redistribution of elements between the phases without new phase formation. The oxygen mobility and reactivity of powdered LBM, BYS and composites were estimated by the oxygen isotope exchange (using both static and flow (SSITKA) modes) and O-2 TPD, while weight relaxation technique was applied for studies of oxygen mobility in dense composite pellets. The oxygen mobility of composites was shown to increase with sintering temperature exceeding additive level, which suggests a positive role of interfaces as fast oxygen migration paths. For best LBM + BYS composites, the value of the oxygen chemical diffusion coefficient exceeds that of well known LSFC-GDC composite. (C) 2013 Elsevier B.V. All rights reserved.