Browsing by Author "Shaula, AL"

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    Oxygen permeability, thermal expansion and stability of SrCo0.8Fe0.2O3−δ–SrAl2O4 composites
    (Elsevier, 2007-07-15) Yaremchenko, AA; Kharton, VV; Avdeev, M; Shaula, AL; Marques, FMB
    Additions of SrAl2O4 phase to mixed-conducting SrCo0.8Fe0.2O3−δ promote oxygen-vacancy ordering and brownmillerite formation at temperatures below 1050 K due to Al3+ incorporation, but also decrease thermal expansion coefficients (TECs) and improve thermal shock stability. The SrCo0.8Fe0.2O3−δ–SrAl2O4 composite membranes exhibit also a relatively high stability with respect to interaction with CO2 due to A-site deficiency of the perovskite-related phase, caused by partial SrAl2O4 dissolution. The oxygen permeability and electronic conductivity of (SrCo0.8Fe0.2O3−δ)1−x(SrAl2O4)x (x=0.3–0.7) composites are determined by the perovskite component and decrease with increasing x. Despite minor diffusion of the transition metal cations into SrAl2O4, hexagonal above 940 K and monoclinic in the low-temperature range, this phase has insulating properties. Nonetheless, at x=0.3 the oxygen permeation fluxes at 1073–1173 are similar to those through single-phase SrCo0.8Fe0.2O3−δ membranes. The average TECs of the composite materials, calculated from dilatometric data in air, vary in the ranges (10.0–11.3)×10−6 K−1 at 300–900 K and (14.7–21.1)×10−6 K−1 at 900–1100 K. The low-p(O2) stability limit and electronic transport properties of SrCo0.8Fe0.2O3−δ are briefly discussed. © 2007, Elsevier Ltd.