Formation of Al₂O₃-BaTiO₃ nanocomposite oxide films on etched aluminum foil by sol-gel coating and anodizing

Barium titanate BaTiO₃ (BT) sol was dip-coated on the etched aluminum foils by a sol-gel process. After annealed at 600 °C in air, the foils were anodized in ammonium adipate solution. The voltage-time variations during anodizing were monitored. The structure, composition, and electric properties of the anodic foils were investigated. The obtained foils were fabricated into aluminum electrolytic capacitors and the load and shelf life test were measured. It was found that the slope of the voltage-time curve of aluminum foil covered with BT films became steeper. A triple layer of Al/Al ₂O₃/BT was formed after anodizing Al/BT foil. The specific capacitance and the product of specific capacitance and withstanding voltage of anodic foil with a BT coating were about 46.36% and 38.90% larger than that without a BT coating. After the load life and shelf life of 2500 h at 85 °C, two kinds of capacitors have similar behaviores and meet with Nichicon standard of Japan. From the results, BaTiO₃ is promising to be used as the dielectric of aluminum electrolytic capacitor to increase the specific capacitance.