Two-Phase-Interfaced, Graded-Permittivity Titania Electrical Insulation by Atmospheric Pressure Plasmas

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 ε_r. Here, we address these issues by interfacing the rutile and anatase TiO₂ layers on a ceramic with very different ε_r 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.