Structural and Optical Properties of Sr-Modified Bismuth Silicate Nanostructured Films Synthesized by Sol Gel Method

In this work, the effects of strontium addition on the structure and optical properties of nanostructured bismuth silicate (Bi4Si3O12) thin films prepared via sol-gel were studied. At first, different sols containing the optimum ratio of precursors were synthesized, and then, the prepared sols were coated on the substrate via dip coating. The dip coated samples were dried at 100oC and, in order to obtain the crystalline structure, calcination was done at 700 oC for 1 h. The prepared thin films were characterized and analyzed via scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), atomic force microscope (AFM), and X-ray diffraction (XRD) analyses as well as ultraviolet-visible spectroscopy. The results showed that a homogeneous coating of bismuth silicate with the grain size in the range 35-50 nm could be formed. XRD analysis demonstrated the annealed sample at 700 oC composed of crystalline Bi4Si3O12 phase without any secondary phase. Investigation of the optical properties of the prepared thin films revealed that the addition of strontium decreased transparency from 82 to 78% and band gap from 3.61 to 3.32 eV.