Transparent thin films of Bi2WO6, Bi4Ti3O12 and Sr0.75Ba0.25Nb2O6

Transparent thin films were prepared by a sol–gel method starting from precursor formation in solution, subsequent spin coating followed by a heating ramp up to a maximum of 700 °C. Starting from a Bi₂MoO₆ synthesis route, the phase formation and thin film processing of the bismuth containing materials Bi₂WO₆, Bi₃Ti₄O₁₂ and additionally of the tungsten–bronze structure Sr_0.75Ba_0.25Nb₂O₆ were studied. Spin coating was used to adjust the film thickness in a wide range from 6 to 200 nm. All films were obtained as multicrystalline pure phases according to X-ray diffraction analyses. Scanning electron micrographs revealed homogeneous coatings composed of nanoparticles with a crystallite size varying between 20 and 100 nm, furthermore the UV–VIS spectra demonstrated a high transparency of the films, 80–90% at 600 nm.