Effect of different complexing agents on the magnetic, optical and photocatalytic properties of sol–gel synthesized KBiFe2O5

Polycrystalline samples of potassium bismuth ferrite (KBiFe2O5) were synthesized using sol–gel technique employing different complexing agents, like citric acid, maleic acid, sucrose and tartaric acid. Investigation on the influence of different complexing agents on the magnetic, optical and photocatalytic properties of KBiFe2O5 (KBFO) were carried out. X-ray diffraction studies revealed that the pure phase KBiFe2O5 was formed at the calcination temperature of 600°C for complexing agent, sucrose and tartaric acid, whereas in case of the sample prepared using citric acid and maleic acid as complexing agent some impurity peaks were observed. The samples prepared using different complexing agents at 700°C gave pure KBFO polycrystalline samples. So 600–700°C is the suitable calcination temperature for the formation of single-phase KBFO. These results are also confirmed from the thermo-gravimetric and differential scanning calorimetry analysis carried out on the KBFO precursors. It was also observed that the complexing agent has significant influence on the magnetic properties of the material. Maximum induced magnetization of 0.605 emu g−1 has been observed for the sample prepared using tartaric acid at the calcination temperature of 600°C and also magnetization saturated for the maximum applied field of 15 kOe, whereas sample prepared with sucrose as the complexing agent under similar condition did not show saturation in the magnetization and gave magnetization value of 0.096 emu g−1 for the applied filed of 15 kOe. This difference is attributed to the particle size difference obtained with different complexing agents. For the single-phase KBFO samples prepared using citric acid, maleic acid, sucrose and tartaric acid at calcination temperature of 700°C, the magnetization values are 0.08, 0.0561, 0.044 and 0.0471 emu g−1, respectively. Optical properties of the samples were studied using diffuse reflectance spectroscopy. All the samples exhibited strong absorption in the visible region of the solar spectrum and featured a bandgap of 1.75 eV. Evaluation of the visible light-induced photocatalytic activity of pure-phase KBFO was also carried out by degradation of methylene blue as a model pollutant.