Electrical Characterization of Thermally Sprayed Insulating Ceramic Coatings

Thermally sprayed ceramic coatings (e.g. Al₂O₃, MgAl₂O₄) can be used as electrically insulating materials for example in high temperature applications (e.g. fuel cells) or in other demanding conditions where ceramic-based materials in complicated structures are needed instead of e.g. polymers. In general, relatively few studies of the dielectric properties of thermally sprayed ceramic coatings can be found in literature and further analysis is thus needed. This paper focuses on the characterization of dielectric properties of thermally sprayed ceramic coatings. The influence of breakdown strength measurement arrangements on the results is presented as well as the effects of ambient conditions on the dielectric properties of a coating. Also, the behavior of certain materials during dc resistivity measurements is shown and the best measuring procedures are discussed. The influence of microstructural features (e.g. porosity and lamellar structure) on the dielectric properties of the studied coatings will also be analyzed and presented.