Andreas Hospach

Deposition of La1−xSrxFe1−yCoyO3−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 A1−xA′xB1−yB′yO3−δ have received considerable attention as candidates for oxygen separation membranes. Preparation of La1−xSrxFe1−yCoyO3−δ (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−xCoxO4, 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.

Investigation of Vapor Phase Deposited Columnar Plasma Spray Coatings

Abstract The relatively new PS-PVD method (Plasma Spray – Physical Vapor Deposition) allows for an almost complete evaporation of the spray powder by means of a high energy input and a low ambient pressure. On the substrate to be coated, the spraying material condenses to columnar, feather-like structured layers as are known from the EB-PVD process (Electron Beam – Physical Vapor Deposition). These layer structures are of interest in applications in which high strain tolerances are required, such as for thermal barrier coatings in gas turbines where cyclic heating and cooling of the coatings takes place. Courtesy of the high growth rate, PS-PVD can represent a more cost-effective alternative to EB-PVD. The main difference compared to EB-PVD coatings is the higher porosity of the PS-PVD coatings. However, this higher porosity leads to difficulties during the preparation when coatings are characterized. This publication describes how YSZ-coatings (Yttrium-stabilized zirconia) produced by means of PS-PVD are characterized with regard to specific surface area, density, pore distribution, hardness, and sintering activity and compared with EB-PVD coatings.