Synthesis, structures and photocatalytic activities of microcrystalline ABi2Nb2O9 (A=Sr, Ba) powders

Microcrystalline ABi2Nb2O9 (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. The as-prepared samples were characterized by the X-ray diffraction technique, BET surface area analysis, UV–vis diffuse reflectance spectrum, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-atomic emission spectrometry. The results indicated that single-phase orthorhombic SrBi2Nb2O9 could be obtained after being calcined above 650 °C, while BaBi2Nb2O9 was tetragonal. Based on the diffuse reflectance spectra, the band gaps of the obtained samples were calculated to be around 3.34–3.54 eV. For the photocatalytic redox reaction of methyl orange under UV-light irradiation, SrBi2Nb2O9 exhibited higher photocatalytic activity than that of BaBi2Nb2O9. The effects of the crystallinities, BET surface areas and crystal structures of the samples on the photocatalytic activities were discussed in detail.