Chitosan-assisted hydrothermal synthesis of multiferroic BiFeO3: Effects on structural, magnetic and optical properties

Abstract

BiFeO3 is the only multiferroic materials that present both spontaneous magnetic and electric polarizations at room temperature. However, the weak magnetization (almost zero) have been measured in bulk BiFeO3 materials which prevent it to be applied in multiferroic based devices. Therefore, the modification on the crystal structure of BiFeO3 materials are required to enhance its magnetization. In this work, for the first time BiFeO3 materials with and without Chitosan are successfully synthesised via a hydrothermal process. The X-ray diffraction data for both samples indicated that the samples have a single phase belonging to R3c space group with perovskite rhombohedral structure. Moreover, Rietveld refined X-ray diffraction (XRD) analysis suggested significant changes in the crystal structures of BiFeO3 with the addition of Chitosan. Scanning Electron Microscope (SEM) also demonstrated different morphologies of BiFeO3 where the sizes of the BiFeO3 is suggested to increased with the addition of Chitosan. Furthermore, UV–vis absorbance characterisation estimated the value of a direct energy band gap at 1.35 eV and 1.16 eV for BiFeO3 and Chitosan-assisted BiFeO3, respectively. The magnetisation of multiferroic BiFeO3 also improved when Chitosan was introduced in the hydrothermal process.