Synthesis and microstructural characterization of Bi12SiO20 (BSO) thin films produced by the sol–gel process

We have produced Bi12SiO20 (BSO) thin films using the sol–gel process. The stable sol was synthesized using Bi(NO3)3·5H2O and Si(OC2H5)4 (TEOS) as the precursors, acetic acid and 2-ethoxyethanol as the solvents, and ethanolamine as the stabilizer. The stability of the solution, which depends on the concentration and the Rh value (Rh = [H2O]/[M]), directly affects the microstructure of the BSO thin film. We determined that the optimal concentration for the preparation of BSO thin films is 0.76 M. The influences of the substrates, the annealing temperature, the concentration and the Rh = value of the solution on the microstructure of the Bi12SiO20 thin films were investigated. X-ray diffraction (XRD) showed that the Bi12SiO20 starts to form at 500 °C and that single-phase Bi12SiO20 polycrystalline thin films are formed at 700 °C. The coated films were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM).