Preparation and characterization of powders and thin films of Bi2AlNbO7 and Bi2InNbO7 pyrochlore oxides

Powders and thin films of Bi2InNbO7 and Bi2AlNbO7 with pyrochlore-type structures were prepared by metalorganic decomposition processes (MOD). The structural evolution of the powders was characterized by X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). The powders were obtained at lower temperatures and faster than with conventional solid-state reactions. The films were further characterized by ultraviolet–visible–near-infrared (UV–vis–NIR) absorbance spectroscopy and atomic force microscopy (AFM). A pyrochlore-type phase in the films was obtained at even lower temperatures than the powders. These presented high transmittances in the vis–NIR range, uniform thicknesses and low roughnesses. A blue shift in the optical gap was observed as the thickness decreased. This was mainly attributed to the Brus effect, since the films showed the presence of nano-sized clusters. The film properties make them very interesting for technological applications such as in photocatalytic processes.