Synthesis of barium titanate films by plasma electrolytic oxidation at room electrolyte temperature

Crystalline barium titanate films were directly synthesized onto Ti plates by plasma electrolytic oxidation at room temperature using barium acetate and 2 M NaOH as electrolytes. The effect of the concentration of barium acetate ranging from 0.05 M to 0.5 M on the synthesis of BaTiO3 was investigated. XRD results showed that the formation of BaTiO3 required a minimum of 0.1 M barium acetate. The electrolytic voltage was controlled at voltages below 85 V to avoid film deterioration by the intense arcing. The current-time curves indicated that intermittent spark discharges were initiated at about 60 V and continued to above 80 V. SEM results revealed the crater-shaped and grained cubic phase barium titanate films formed by plasma electrolytic oxidation. Surface roughness could be greatly reduced by about one order of magnitude by decreasing electrolytic temperature from 55 °C to room temperature. The thickness of the films could reach 20 μm and the dielectric constant could reach 1240 at frequency of 100 Hz.