Effect of Preparation Routes on the Crystal Purity and Properties of $$\hbox {BiFeO}_{3}$$ Nanoparticles

Abstract

Sol–gel as a chemical solution deposition technique is compatible with functional device fabrication technology. Single-phase bismuth ferrite ( $$\hbox {BiFeO}_3$$ ) mutiferroic with its multi-functionality has extensively been studied for a variety of prospective novel device applications. However, the synthesis of $$\hbox {BiFeO}_3$$ is confronted with a challenge to produce pure state without any secondary phase. Scarcity of unified process parameters impede justification of best synthesis techniques. In this work, sol–gel methods with and without auto-combustion reactions were used to synthesize bismuth ferrite ( $$\hbox {BiFeO}_3$$ ) nanoparticles. Different techniques UV–Vis–NIR spectroscopy, XRD, EDS, and SEM were used to investigate the effect of preparation routes on the crystal purity and properties of prepared samples. Synthesized nanoparticles were calcined at temperature between 400 and 800 $$^{\circ }$$ C and an optimal calcination temperature was found to be 600 $$^{\circ }$$ C. Band-gap was determined by UV–Vis–NIR spectroscopy and found to vary from 1.93 to 2.07 eV. X-ray diffraction (XRD) has confirmed single phase rhombohedral crystal structure with R3c symmetry. Avg crystallite size was found to be higher (40–68 nm) in auto-combustion reaction compared to that of 23–42 nm obtained in sol–gel method without auto-combustion reaction. The band-gap energy was found to reduce with decreasing crystallite size (above the critical size of 10 nm) following Brus’s effective mass model. Induced strain was found to exhibit an inverse relation with crystallite size and displayed substantial reduction in auto-combustion reaction route. The microstructural features were investigated by field emission scanning electronic microscopy and avg particle size was shown to vary from 107 to 197 nm depending on adopted synthesis route. A low reaction temperature (70 $$^{\circ }$$ C–80 $$^{\circ }$$ C) without auto-combustion and calcination temperature at $$600^{\circ }$$ C were found to be optimal conditions for the preparation of low impurity un-doped bismuth ferrite nanaoparticles.