Formation of BaTiO3 thin films from (110) TiO2 rutile single crystals and BaCO3 by solid state reactions

The formation of BaTiO3 thin films from (110) TiO2 rutile single crystals and BaCO3 was investigated experimentally by solid–solid and gas–solid reactions in vacuum. X-ray diffraction revealed the formation of an intermediate Ba2TiO4 phase before BaTiO3 is formed. According to our calculations the formation of Ba2TiO4 is associated with a maximum decrease in the Gibbs energy at a CO2 pressure lower than 10− 4 mbar. Reactions at 600–900 °C showed different processes to occur in the solid–solid and gas–solid reactions. The observations are interpreted in terms of the different mass transport mechanisms involved. The results shed new light on the phase sequence during BaTiO3 formation; in particular a dissociation of BaCO3 prior to its participation in the reaction has become rather unlikely.