Theoretical modeling and experimental verification of electrochemical equilibria in the Ba-Ti-C-H2O system

The thermodynamic principles controlling the electrochemical synthesis of b arium titanate (BaTiO3) films are discussed and explored. a variety of E-h- pH diagrams were generated for the Ba-Ti-C-H2O system as a function of temp erature and whether CO2 was in the system. Barium titanate is predicted to form at 25 degrees C and higher temperatures under alkaline conditions. It is demonstrated that the phase field for BaTiO3 enlarges as a function of p H with increasing temperature in the absence of CO2. The role of CO2, altho ugh still important in controlling the phase stability of BaTiO3 via the fo rmation of BaCO3, becomes less important under solution pH conditions great er than pH similar to 13 and temperatures greater than 100 degrees C. The t heoretical Eh-pH predictions compare favorably with experimentally determin ed regimes, where BaTiO3 and films in the Ba-Ti-C-H2O system form through e lectrochemical reactions.