Effect of La doping on the ferroelectric and optical properties of BiFeO3: a theoretical-experimental study

Much work has been done already on pure and doped BiFeO3 (BFO), however, renewed interest has emerged when considered as a viable photovoltaic material. It has been shown that, for this purpose, spontaneous polarization and energy gap are relevant physical quantities. In this theoretical-experimental work, we have studied the possibility of enhancing the spontaneous polarization and reducing the BFO bandgap by replacing 10% of the site A ions of the perovskite structure with La. The structural, electronic and optical properties of (Bi0.9La0.1)FeO3 were investigated using pristine BFO as a reference. A rhombohedral crystal structure was determined after La substitution and its corresponding bandgap of 2.49 eV was smaller than that of pure BFO. Theoretically, the spontaneous polarization (Ps) of the BFO increased with the incorporation of La up to a value of 103 C cm−2, showing its effect on the ferroelectric properties. Moreover, the theoretical results and experimental measurements of the optical properties demonstrated the reduction of the optical gap.