17 Synthesis and Characterization of Bismuth Ferrite Nanoparticles Anoopshi Johari Department of Physics, National Institute of Technology, Kurukshetra 136119 Haryana anoopshi.akg@gmail.com OF ADAPTIVE VOLTERRA FILTERS __________________________________________________________________________________________________________ .Abstract--In the present work, Nanoparticles (NPs) of multiferroic bismuth ferrite (BiFeO 3 ) were synthesized via a wet chemical route using bismuth nitrate and iron nitrate as starting materials and excess citric acid as chelating agent, respectively, followed by thermal treatment at 350 ∘ C, 450 ∘ C and 550 ∘ C. It was found that BiFeO 3 nanoparticles crystallized at 350 ∘ C when using citric acid as chelating agent. BiFeO 3 nanoparticles with different sizes distributions show obvious ferromagnetic properties, and the magnetization is increased with reducing the particle size. The prepared samples were characterized by X-ray diffraction of powder (XRD), scanning electron microscope (SEM) for extracting their surface morphology and their crystallographic structure. The surface morphology studies confirm the growth of bismuth ferrite nanoparticles with their diameters in the range of 200nm to 500nm. The XRD analysis concludes the rhombocentered structure of synthesized nanoparticles. Keywords: Bismuth ferrite, Nanoparticles, X-ray diffraction I. INTRODUCTION BISMUTH Ferrite (BiFeO 3 , BFO) is one of the very few multiferroic materials with a simultaneous coexistence of ferroelectric with high Curie temperature (T C = 810-830˚C) and anti-ferromagnetic order (below T N = 370˚C) parameters in perovskite structure. However, these two ordering parameters are mutually exclusive in principle because ferroelectricity and magnetism require different filling states of d shells of transition metal ions. Empty d shells mainly exist in ferro-electricity, while partially filled d shells are required in magnetism. Therefore multiferroic are rare and it exhibits weak magnetism at room temperature. Though BFO was discovered in 1960, recently there is a renewed interest because of its possible novel applications in the field of radio, television, microwave and satellite communications, audio-video and digital recording and, as permanent magnets. So far, bismuth ferrite powders have been prepared by the solid-state methods (classic [1, 2] and mechano-chemical ones [3] and solution chemistry methods (such as precipitation/co precipitation [4], sol–gel [5, 6] hydrothermal [7] and sonochemical [8] ones). Most of the mentioned procedures need high temperature treatments (>800°C). Due to the requirement of nanosized oxides and in order to avoid bismuth volatilization the developing of low temperature synthesis methods is essential [9]. Previous studies have demonstrated that synthesis of Bismuth Ferrites nanoparticles through a traditional solid-state method produces poor reproducibility and causes formation of coarser powders as well as Bi 2 O 3 /Bi 2 Fe 4 O 9 impurity phase [7], [8]. Up to date, several chemical routes (for example: hydrothermal treatment, mechano-chemical synthesis method, and sol-gel methodology, etc.) have been successfully employed for fabricating BFO nanoparticles. However, these approaches have certain shortcomings such as impurities in the final products [9]. In the present work, Bismuth ferrite (BiFeO 3 ) nanoparticles are successfully synthesized using citric acid. The sythesized bismuth ferrite (BiFeO 3 ) nano-particles were characterized by X-Ray Differaction (XRD) and Scanning Electron Microscope (SEM) for extracting their surface morphology and crystal structure. II. EXPERIMENTAL PROCEDURE In the present work, sol-gel method is used. For the synthesis of bismuth ferrite nano-particles, bismuth nitrate [Bi(NO 3 ) 3 ·5H 2 O] and iron nitrate [Fe(NO 3 ) 3 .9H 2 O] were weighed and dissolved in de-ionized water to make a solution of 0.2M. Afterwards some amount of diluted nitric acid (65% to 68% HNO 3 ) was added to the mixture. Then citric acid (C 6 H 8 O 7 ) was added to the solutions, this act as chelating agent. The light-yellow-colored solution was heated under vigorous stirring. The beaker with solid deposit was kept in the oven at 150˚C. Powders were quarterly divided and calcinated in the oven at 350˚C, 450˚C, and 550˚C respectively, to obtain well crystallized Bismuth Ferrites nano-particles with controllable sizes [10]. After the complete chemical synthesis and heat treatment of the synthesized products, the sample were characterized using X-ray diffraction (XRD) with a X-ray diffractometer with Cu Kα radiation (λ = 0.154178 nm) and Scanning Electron