Low temperature synthesis of high purity nanoscaled BiFeO3 by a fast polymer solution method and their ferromagnetic behavior

Abstract

The main obstacle in synthesizing bismuth ferrite is the presence of secondary phases. This paper presents the results of the effect of an unusual chelating agent (polyacrylic acid) on the synthesis of pure and very crystalline BiFeO3 (BFO) nanoparticles. The common chelating system citric acid/ethylene glycol was also evaluated here. The structural (X-ray diffraction and Raman spectroscopy), microstructural and magnetic characteristics were studied. The high resolution XRD confirmed the high purity (>96% in 500 °C) and very crystalline nanoparticulate BFO, without adding any excess of Bi2O3 during the synthesis neither later steps to eliminate secondary phases, i.e., acid leaching or thermal treatment. Thus, the high effectiveness of polyacrylic acid (PAA) as a novel chelating agent in BFO initial crystallization yielded the BFO phase at a temperature lower than that reported in the literature. The nanoparticles (NPs) show a distorted R3c lattice, due to the deformation effect markedly at the lower temperature of synthesis (350 °C), diminishing as the synthesis temperature increases. Raman spectra confirmed the R3c ferroelectric phase of BFO nanoparticles. Room temperature magnetic measurements showed a remarkable ferromagnetic behavior, with a visible saturation magnetization as a result of the small particles.