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1273 |
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Phase stability and structure of conductive perovskite
ceramic coatings by thermal spraying |
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Juha Lagerbom* / VTT Technical research center of finland, Finland Ulla Kanerva / VTT, Finland Antti-Pekka Nikkilä/ Tampere University on technology , Finland Tommi Varis/ VTT, Finland Mikko Kylmälahti/ Tampere University on technology , Finland Petri Vuoristo/ Tampere University on technology , Finland |
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Perovskites are considered as potential materials in solid oxide fuel cells (SOFC) for different reasons at different parts of the fuel cells. Perovskites such as La0.8Sr0.2MnO3 (LSM) and other compositions are electrically conductive which is necessary for SOFC applications. One possible application is protection coating for interconnect plates (bipolar plate) to avoid chromium oxide evaporation from the surface of ferritic stainless steel. Different commercial and experimental perovskite powders were sprayed by plasma and HVOF spraying under different spray conditions. Spraying of pervoskites was found to be challenging and required careful parameter optimization in both spray methods. Microstructure, phase structure and electrical conductivity of the coatings were investigated. A very fine crack structure, possibly caused by low mechanical strength and ductility of the compounds, was easily formed in coatings prepared by plasma and HVOF spraying. Spraying method, parameters and spraying atmospheres were found to affect the stability of the perovskite compounds due to low chemical stability at high spray temperatures. Oxygen deficiency or oxygen surplus was concluded to cause distortion of the compounds crystal structure, causing thus shifting of XRD-peaks due to change of lattice parameters. Electric conductivity was affected by the crystal structure. |