Formation of the mixed oxide consisting of and was studied by the DTA/TGA technique and x‐ray diffraction. The coating agent containing and tetra‐n‐butyl titanate converted into the mixed oxide of and at about 400°C on the Ti substrate, and the reaction was exothermic. The electric resistance through the oxide film depends much on the fire temperature, and an optimum condition arises between 450° and 500°C. The solution composition and the time of preparation are also important factors. The anodic polarization behavior in the solution was also affected by the material or the condition of preparation of the oxide‐coated Ti electrode.