Optimal Doping Level of Iron in Bismuth Titanate for Oxide Optoelectronics

Abstract

A series of Fe-doped Lanthanum-modified Bismuth Titanate (Fe-BLT) based powders was synthesized by conventional solid reaction methods with increasing amounts of Fe atoms substituting Ti atoms. We conducted X-ray diffraction (XRD) analysis and found that all samples crystallized with an orthorhombic structure. The size distribution and morphology of the Fe-BLT samples were observed by using scanning electron microscopy (SEM). The absorption spectra of the Fe-BLT based powders obtained from ultraviolet-visible spectroscopy (UV-Vis) showed that the optical bandgap decreased from 2.42 eV to 1.93 eV as a result of the substitution of Fe atoms. The results of the XRD and SEM measurements with the UV-Vis spectra indicate that no Fe-based secondary phase contributed to the reduction of the optical bandgap. Therefore, we conclude that substitutional iron atoms are responsible for modifying the electronic structure of bismuth titanate based oxides. The optical bandgaps of the series of iron doped samples did not decrease linearly with increasing nominal Fe content in the powder. This indicates a small amount of Fe is sufficient to tune the bandgap to the requisite values. The simple alloying approach for controlling bandgap developed here could be applied to other complex oxides materials for use in emerging optoelectronic and energy applications.