Comparison of Ceramic Insulation Coatings via Impedance Spectroscopy

Abstract

Alumina is often used for electrical insulation. However, different material systems promise to increase the insulation due to their material characteristics. Because of the process properties including high cooling rates, thermally sprayed coatings generally differ from sintered material, which also effect the electrical properties. Within this study, different thermally sprayed coatings are analyzed via impedance spectroscopy to evaluate the capacitive and the electrical insulation behavior. Besides comparing the frequency-dependent resistance, equivalent circuit diagrams were used to calculate the relative permittivity of the coatings. X-ray diffractograms reveal the phase stability of the coatings during thermal spraying. X-ray diffraction was additionally conducted to classify the systems and the respective effects. In particular, the investigated mullite-based coatings exhibit slightly increased impedance values compared to conventionally used alumina-based coating systems.