Tunable band gap of iron-doped lanthanum-modified bismuth titanate synthesized by using the thermal decomposition of a secondary phase

Abstract

The photoelectric properties of complex oxides have prompted interest in materials with a tunable band gap because of the absorption. The substitution of iron atoms in La-modified bismuth titanate (BLT) can lead to dramatic improvements in the band gap; however, the substitution of iron atoms while maintaining the original bismuth layer structure without forming a BiFeO₃ secondary phase is quite challenging. Therefore, a series of Fe-doped BLT (Fe-BLT) samples were synthesized using a solid reaction at various calcination temperatures (300 ∼ 900°C) to remove the secondary phase. The structural and the optical properties were analyzed by using X-ray diffraction and ultraviolet-visible absorption spectroscopy. This paper reports a new route by using high-temperature calcination, to synthesize the Aurivillius phase with a reduced optical band gap due to the thermal decomposition of BiFeO₃ during high-temperature calcination. This simple route to reduce the second phase can be adapted to other complex oxides for use in emerging oxide optoelectronic devices.