Study on the microstructural evolution of BaTiO3 on titanium substrate during MAO

Thin barium titanate film was fabricated on Ti substrate by means of alternative current (AC) micro-arc oxidation (MAO) in Ba(OH)2 alkaline solution. Using XRD, SEM EDS, and TEM, microstructure evolution during MAO and effect of heat-treatment on microstructure of the film were investigated. In 0.2 mol/l Ba(OH)2 solution and current density of 2–5 A/cm2, combination of amorphous phases, cubic and hexagonal phases of BaTiO3 exist in the as-prepared film. Some of cubic phases of BaTiO3 are derived from amorphous phases during MAO. When annealed at above 900 °C for 8 h, the amorphous phases are crystallized. It is difficult to obtain tetragonal phase of BatiO3 directly by AC MAO, even annealed at 1200 °C for 8 h.