Microwave dielectric properties of low power plasma sprayed NiCrAlY/Al2O3 composite coatings

NiCrAlY/Al2O3 composite coatings were prepared using the low power atmospheric plasma spraying technique. The metal fillers existing in the form of particles and lamellar are randomly distributed within the alumina matrix, which can be confirmed by scanning electronic microscopy. Dielectric measurement showed a significant enhancement of complex permittivity for NiCrAlY/Al2O3 composite coatings with the increase in NiCrAlY content over the frequency range 8.2–12.4 GHz. Both the real (ε′) and imaginary (ε″) parts of the complex permittivity increase with increasing NiCrAlY content, which is ascribed to interfacial polarization and conductance loss, respectively. Furthermore, strong frequency dispersion was observed for the composite coatings with 36 wt.% NiCrAlY.