Improvement of Ba0.5Sr0.5Co0.8Fe0.2O3−δ functional properties by partial substitution of cobalt with tungsten
2014
Popov, M.P. | Starkov, I.A. | Bychkov, S.F. | Nemudry, A.P.
The work deals with the studies of Ba0.5Sr0.5Co0.8−xWxFe0.2O3−δ (х=0–0.1) materials obtained by the partial substitution of cobalt in Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) by tungsten. It is shown by means of XRD that the solubility limit of tungsten in the structure of cubic perovskite BSCF is about 2%<x<3%. Continuous equilibrium «3−δ−lgpO2−T» diagrams obtained by oxygen release technique are presented for the compositions BSCF and Ba0.5Sr0.5Co0.78W0.02Fe0.2O3−δ (BSCFW2) for the first time. The diagrams allowed us to detect the new phase transition P1 (low temperature phase, Pm3¯m) – P2 (high-temperature phase, Fm3¯c). It is demonstrated that Co substitution by highly charged cation W+6 (2%) improves the functional properties of BSCF; increases the oxygen permeability, suppresses phase transition «cubic–hexagonal» perovskite, enhances the stability of membrane material in the atmosphere of CO2, which provides the long-term stability of oxygen fluxes. The dependence of oxygen fluxes on membrane thickness provides evidence that for L≥1.60mm oxygen permeability is limited by the bulk diffusion of oxygen ions.
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