Al2O3–(Ba0.5Sr0.5)TiO3 composite oxide films on etched aluminum foil by sol–gel coating and anodizing

(Ba0.5Sr0.5)TiO3 (BST) coating was applied to the etched aluminum foils by sol–gel dip-coating with (Ba0.5Sr0.5)TiO3 sol prepared by mixing tetrabutyl titanate, barium acetate, strontium acetate, diethylene glycol, acetic acid and distilled water. After annealing under 500–600 °C in air, Al2O3–BST composite oxide film was formed on the surface of the etched aluminum foil by anodizing galvanostatically in a neutral adipite and borate solution. The BST powders annealed under different temperatures were characterized by TG–DTA and X-ray diffraction (XRD), and the specific capacitance of the coated samples annealed under different temperatures and times was measured. It was experimentally shown that the specific capacitance of the samples with BST coating is greater than without BST coating. The composite films are promising to be used as the dielectric of electrolytic capacitor.