Relationship between dielectric strength and mechanical properties of alumina films fabricated by aerosol deposition

Aerosol deposition (AD) is a promising technique for preparing insulation coatings because it allows for the room-temperature fabrication of dense films with micrometer thickness. However, films fabricated by AD are composed of tiny crystallites on the nanometer scale and contain many grain boundaries, and their insulating performance is not clear. In this study, the dielectric strength, nanoindentation hardness, and residual stress of alumina films fabricated by AD were investigated. Dielectric strengths as high as 200 kV mm � 1 were achieved, which corresponds to excellent performance in the thickness range of 1-100 mu m compared to other coating techniques. The dielectric strength tended to increase with increasing hardness and compressive residual stress, which was rationalized in terms of the grain size and grain boundary density.