Experimental and first principles investigation of Bi1-xCexFeO3: Structure, electronic and optical properties

The effects of Ce substitution on the structural, electronic and optical properties of BiFeO3 (BFO) powders using a simple hydrothermal method were investigated. X-ray diffraction data and scanning electron microscope images reveal the lattice contraction and decrease of grain size for the Bi1-xCexFeO3 (BCFO) powders. The absorption in ranges of 250-900 nm is enhanced with the increase of Ce dopant. The optical band gap of BCFO powders extrapolated by the UV-Vis absorption data decreases from 2.69 (x = 0, pure BFO) to 2.39 eV (x = 15%), in good agreement with the first principles calculation. We further demonstrated that the tunable gaps were mainly attributed to the doped Ce-4f states. An additional peak shifted from 1.45 to 1.65 eV in the calculated absorption spectrum is owing to the intraband transition between the Ce-4f impurity band and Fe-3d states or O-2p states in the conduction band, indicating that the band gap can be adjusted in another band range. The two tunable bands will open a new avenue to discover and design optimal BFO compounds for optical applications.