Electrochemical study of the formation of thin BaTiO3 films

Thin BaTiO3 films have been produced on Ti by the hydrothermal‐electrochemical method, using a 0.25 M Ba(OH)2 electrolyte at 150 °C. The film growth is limited initially by the charge transfer involved in Ti oxidation. As the film grows, the ionic diffusion through the film becomes the limiting process. The diffusion coefficient (D≊10−8 cm2/s) is between the expected values for aqueous solutions and solid state, suggesting that the film through which barium diffuses is not a completely crystallized phase. In the electrochemical‐hydrothermal process the nucleation and growth rate can be controlled through the degree of anodical polarization of the titanium electrode. Use of an initial overpotential pulse leads to smaller crystal size and a more even morphology.