Investigation of multiferroic and photocatalytic properties of Gd doped BiFeO3 prepared by hydrothermal technique

Abstract

Bismuth ferrite, BiFeO3 (BFO) and 10% Gd doped BiFeO3 (BGFO) materials were synthesized by using hydrothermal (HT) process at 120°C-200°C reaction temperatures. For the comparison, BFO bulk polycrystalline sample was also prepared by using conventional solid state reaction (SSR) technique. The structural analysis and phase identification of these multiferroics were performed by analyzing X-ray diffraction pattern. The perovskite structure was not formed in hydrothermal process at 120°C, 140°C for BFO and 160°C for BGFO samples. The Rietveld refinement analysis confirmed the high phase purity and lower Fe-O-Fe bond angle for hydrothermally prepared BFO sample at 160°C reaction temperature. The Rietveld refinement also revealed that the all diffraction peaks matched well with the rhombohedral structure (wt. 100%) of pure BFO (R3c space group) prepared at 160°C temperature. FESEM images and their respective histograms demonstrated that the particle size of BFO in hydrothermal method decreases with the decreasing temperature and the average particle size was the smallest for the hydrothermally prepared BFO samples at 160°C reaction temperature. The average particle size of BGFO samples at different reaction temperatures was also notably smaller, however the pure perovskite structure was not formed. Unlike bulk BFO sample the improved magnetization was observed for the hydrothermally prepared BFO nanoparticles. BFO nanoparticles synthesized by HT process at 160C reaction temperature exhibited significantly high saturation magnetization compared to the other samples. The absorption spectra confirmed that the BFO bulk and hydrothermally prepared BFO and BGFO nanoparticles can absorbs light in the visible region. In photocatalytic activity test, the higher photodegradation rate was found for the BFO sample synthesized by HT process at 160C reaction temperature. Due to its good photocatalytic activity and lower band gap for this particular sample generate more than two times of hydrogen than that of bulk BFO as well as commercially available TiO2. The leakage current density of the hydrothermally prepared BFO nanoparticles at 160C reaction temperature was much smaller than that of the bulk BFO and BGFO nanoparticles. The polarization (P) versus electric field (E) hysteresis loops were typical for the hydrothermally prepared BFO sample at 160C reaction temperature compared to the other two samples. The outcome of this investigation demonstrate the improved properties of BFO nanoparticles prepared hydrothermally at significantly low temperature i.e. at 160°C.