Thick alumina dielectric films on aluminum through chemically bonded composite sol–gel

A new process for ∼200 μm thick multilayer dielectric films on aluminum was developed via chemically bonded composite sol–gel. The sol–gel process used alumina and chemical bonding used phosphoric acid and aluminum phosphates. An interlayer was introduced between the coatings and aluminum substrate to decrease the thermal expansion mismatch between the ceramic and the substrate. The dielectric breakdown voltage of about 2500 V was measured for the films at room temperature.