Band gap measurement of Bi₂Mo_xW_1-xO₆ by low loss electron energy loss spectroscopy

This work shows the comparison of high-resolution electron energy loss spectra (HR-EELS) in the low loss region (0−15 eV) to investigate the electronic structure from koechilinite Bi₂MoO₆ to rusellite Bi₂WO₆ varying the stoichiometric relation Bi₂Mo_xW_1−xO₆. The effect of the Mo to W ratio on the bandgap energy was evaluated on individual particles. Two approximations were considered in order to determine the band gap energy value, the first one was a linear fit and the second one was a mathematical fit. Both analyses are in agreement with those ones collected and analyzed by UV–Vis characterization. Our results suggest a direct electronic transition that increases from about 2.53 eV to about 3 eV as the W content increase from 0% to 100% wt. X-ray diffraction was used to corroborate the crystal structure and crystal size; transmission electron microscopy was used to monitor the morphology evolution and UV–Vis spectroscopy in diffuse reflectance mode to determine the Eg. These techniques complement the characterization of these materials.