Synthesis of free-standing crystalline barium titanate films at vapor/liquid or liquid/liquid interface

Synthesis of free-standing crystalline barium titanate (BaTiO3) films at vapor/liquid or liquid/liquid interface at room temperature has been investigated. High concentration Ba, Ti alkoxides precursor solution (1.2 mol/l) or pre-hydrolyzed precursor solutions by water vapor in a H2O/Ba molar ratio of 0 to 6 were used as dropping solutions at the interfaces. Transparent gel films were formed when partially hydrolyzed precursors (H2O/Ba = 2 to 3) were spread out on a N-2/liquid paraffin interface. The films shrank from syneresis and vaporization of the solvent during aging at room temperature. As a result, free-standing transparent films with a thickness of around 1 mum and little stoichiometric deviation were obtained by separation from the liquid surface and rinse by hexane. The films consisted of crystalline BaTiO3 particles of less than a few nanometers. Nanostructured dense BaTiO3 free-standing films with a grain size less than 100 nm were obtained at 1030 degreesC.