State-of-the-art insulator and electrode materials for use in high current high energy switching

An investigation into the failure of ceramic insulators that are used in a surface discharge switch (SDS) was conducted. The materials analyzed are Al₂O₃-25% SiC, MTF (modified alumina titanate), and CZA 500 (zirconia-alumina composite) ceramics. These insulators were subjected to high-current (~300 kA) surface discharges in atmospheric air and nitrogen. Energy-dispersive X-ray surface analysis was performed on the insulator surfaces in order to determine the contaminants that are present and the possible failure modes associated with the plasma arc environments mentioned above. Electrode erosion rates have been measured as a function of total charge transfer (up to 50 C/shot) for several in-situ materials including Cu-Nb, Cu-Nb+LaB₆, and Cu-Ta. Results from comparisons with standard Cu and CuW materials indicate that the in-situ materials represent an efficient method of retaining the copper in the bulk until it vaporizes and thus yield significantly lower erosion rates at high Coulomb transfer rates