Functionally graded materials (FGMs) exhibit unique properties and are expected to deliver outstanding and stable performance under extreme conditions. High-voltage, high-power FGM-based electric insulation commonly fails because of inadequate surface charge control (flashover) performance and stability of stacked layers of dielectric materials with graded permittivity εr. Here, we address these issues by interfacing the rutile and anatase TiO2 layers on a ceramic with very different εr values of 110, 48, and 9, respectively, using scalable, environment-benign, and energy-efficient atmospheric pressure plasma processing. The FGM drastically reduces the maximum electric field along the optimized surface by 66% and increases surface flashover voltage by 36 %, while featuring a remarkable (120/180 days) long-term stability. The mechanisms of the plasma-enabled graded layer formation are presented, which can be used for precise engineering of FGMs for diverse applications in other fields.
Keywords: TiO2; atmospheric pressure plasmas; functionally graded materials; plasma nanofabrication; surface insulation.