Deposition of La1-x Sr x Fe1-y Co y O3-δ Coatings with Different Phase Compositions and Microstructures by Low-Pressure Plasma Spraying-Thin Film (LPPS-TF) Processes

Perovskite-type materials with the general chemical formula A(1-x) A' (x) B1-y B' (y) O3-delta have received considerable attention as candidates for oxygen separation membranes. Preparation of La1-x Sr (x) Fe1-y Co (y) O3-delta (LSFC) coatings by low-pressure plasma spraying-thin film processes using different plasma spray parameters is reported and discussed. Deposition with Ar-He plasma leads to formation of coatings containing a mixture of cubic LSFC perovskite, SrLaFeO4, FeCo, and metal oxides. Coatings deposited at higher oxygen partial pressures by pumping oxygen into the vacuum chamber contain more than 85% perovskite and only a few percent Fe3-x Co (x) O-4, and/or CoO. The microstructures of the investigated LSFC coatings depend sensitively on the oxygen partial pressure, the substrate temperature, the plasma jet velocities, and the deposition rate. Coatings deposited with Ar-rich plasma, relatively low net torch power, and with higher plasma jet velocities are most promising for applications as oxygen permeation membranes.