Nanostructured barium titanate thin films from nanoparticles obtained by an emulsion precipitation method

Spherical non-agglomerated BaTiO3 precursor particles of 3–5 nm size were prepared by an emulsion precipitation method that consisted of the complexation of Ba- and Ti-precursors in separate water-in-decane emulsions, followed by mixing and controlled precipitation upon reactive decomposition of tetramethyl ammonium hydroxide. Stable clear yellow dispersions with a final particle yield of 60% were obtained. In situ high temperature X-ray diffraction (XRD) measurements indicated that the initially amorphous particles crystallised into single-phase tetragonal BaTiO3 at 600 °C. Thin BaTiO3 films of 25–350 nm thickness were prepared from the precursor dispersions by spin coating or controlled deposition on Si wafers. The average crystallite size after annealing at 800 °C was approximately 26 nm, but some larger grains of 100–150 nm size were also observed. Fresnoite (Ba2TiSi2O8) was likely to be formed near the interface between the oxide layer of the Si substrate and the BaTiO3 film.