Study of the structure and mechanical properties of hexagonal BaTiO3 thin films prepared by sol–gel processing

Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray diffraction, atomic force microscopy, nanoindentation technique, and transmission electron microscopy. The results showed that the thin film annealed at 700 °C crystallized with BaTiO3 hexagonal phase and traces of Ba2TiO4 (secondary phase). The nanoparticles and the RMS roughness of the sample treated at 700 °C presented high values when compared with those thermally treated at lower temperatures. The hardness and Youngs’ modulus of the thin films increased with increasing in grain size, and the thin film annealed at 700 °C with crystallite size about 10 nm presented multiple “pop-in” events during nano-indentation loading curves. The annealing temperature, growth size and surface roughness were discussed in connection with the HBT mechanical properties.