High Energy Density Dielectrics for Symmetric Blumleins
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Multilayer, tape cast ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (greater than 10 to the 6th power J/m cubed) and physical size reduction. In particular, symmetric Blumleins are desired with the following properties: High voltage hold off greater than or equal to 300 kV); High, nondispersive permittivity: approxiametly equal to 100 to 900; Ability to be fabricated into various shapes and sizes; Surface flashover inhibition at the edge; Ability to be triggered by surface flashover switching. The compositions being pursued are based on pure BaTiO3 dielectrics. Our approach is to add glass phase additions which result in not only near theoretical densities, but also allow for fabrication of more complex geometries through high temperature creep. Variations in the volume fraction and connectivity of the glassy phase allow for direct control of the permittivity as well as energy density. Structures up to 5" in diameter have been fabricated and pulse-tested at field strengths over 300 kV/cm. A strong dependence of breakdown strength and permittivity has been observed and correlated with microstructure and the glass composition. This paper presents the interactive effects of manipulation of these variables