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High temperature stability of Ba0.5Sr0.5Co0.8Fe0.2O3−d and La0.6Sr0.4Co1−yFeyO3−d oxygen separation perovskite membranes

pubblicazioni - Articolo

High temperature stability of Ba0.5Sr0.5Co0.8Fe0.2O3−d and La0.6Sr0.4Co1−yFeyO3−d oxygen separation perovskite membranes

Sono riportati i principali risultati di un’attività sperimentala finalizzata a caratterizzare i fenomeni e l’entità del degrado di due perovskiti potenzialmente utilizzabili per la realizzazione di membrane per la separazione dell’ossigeno.

The Barium (BSCF) and Lanthanum (LSCF) strontium cobalt–ferrite, are among the most studied mixedionic electronic conducting materials having interesting properties as Oxygen Transport Membranes. Inthis paper the two materials are analysed after long term aging at high temperatures and permeationtests. Several characterisation techniques are used to understand degradation mechanisms. Surface layerswere analysed by X-ray photoelectron spectroscopy: LSCF is stable, while on BSCF a thin layer of carbon-ates forms. Quantitative synchrotron radiation diffraction measurements of hexagonal phase content inaged BSCF allows determining Avrami coefficients at 780, 800 and 820◦C.

This process is associated tothe enrichment of Fe in the regions of grains near the lamellar hexagonal phase, as WDS maps show.Bulk measurements of X-ray Absorption Near Edge Structure (XANES) and the analysis of the Co2p dou-blet in XPS spectra confirm a reduction of Co ions oxidation number after long time at intermediate temperatures.

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