Synthesis of Bismuth Titanate Thin Films by Liquid-Phase Self-Assembled Monolayers

Abstract

Using (NH4)2TiF6, Bi(NO3)3•5H2O and H3BO3 as raw materials, Bi4Ti3O12 thin films were synthesized with liquid phase self-assembled monolayers on the glass substrate. The different precursor solution concentrations and acid contents had the effects on the physical phase and morphology of Bi4Ti3O12 thin films. The Bi4Ti3O12 thin films were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results indicate that the precursor solution with 10.0 mmol/L concentration was prepared by 3:4:9 molar ratio of (NH4)2TiF6: Bi(NO3)3•5H2O: H3BO3 and 6.0 ml acid content, depositing at 50°C for 20h, and heat treating at 590°C for 2h. The as-prepared thin films are well-crystal. The surface is even and dense. The formation mechanism of the Bi4Ti3O12 thin films is as follows: [TiF6-n(OH)n]2- complex ions are formed in the (NH4)2TiF6 aqueous solution. Then H3BO3 continually consumed F- ions of the solution, which made the amounts of [TiF6-n(OH)n]2- ions increase gradually. Under the induction of the electrostatic force, Bi3+ ions and [TiF6-n(OH)n]2- ions would grow naturally on the substrate surface in the form of Bi2[TiF6-n(OH)n]3 or Bi2[TiF6-nOm/2(OH)n-m]3. The samples lost the bound water after the heat treatment and finally the Bi4Ti3O12 thin films with pure phase were obtained.