Dielectric properties of HVOF sprayed ceramic coatings

Thermally sprayed ceramic coatings can be used as electrical insulators for example in high temperature applications (e.g. fuel cells) or in other demanding conditions. In electrical insulation applications the mostly used coating materials are aluminum oxide, magnesium oxide and magnesium aluminate. In general, only few reports of dielectric properties of thermally sprayed ceramic coatings can be found in literature and further analysis is thus needed. In addition, the measurement methods and conditions in previous research are often not fully documented, complicating the evaluation and comparison of the properties of different coatings. The aim of this paper was to characterize dielectric properties of thermally sprayed ceramic spinel coating sprayed with high-velocity oxygen fuel (HVOF) technique. The studied dielectric properties are DC resistivity, DC dielectric breakdown strength, as well as permittivity and dielectric losses at different frequencies. All measurements were made at temperature of 20 °C and at relative humidity of 20 %. Dielectric properties and the composition of coating material are presented and analyzed.