Low-temperature crystallization of barium ferrite nanoparticles by a sodium citrate-aided synthetic process

This article describes the synthesis of barium ferrite nanoparticles at low crystallization temperatures using a sodium citrate-aided process. Monodispersed barium ferrite amorphous nanoparticles were synthesized by the formation of metal−citrate complexes at pH 10, followed by hydrolysis at 100 °C. The mean particle diameter was 4.7 nm with a specific surface area of 137.8 m2/g. This is the first time that sodium citrate has been used as a chelating agent in the synthesis of barium ferrite nanoparticles. Sodium citrate plays two important roles in the process:  it allows the homogeneous mixing of two metal cations in the as-synthesized barium ferrite amorphous nanoparticles, and it retards particle growth via the formation of surface citrate complexes, inhibiting the agglomeration of the nanoparticles. The amorphous precursor nanoparticles were transformed into a hexagonal structure by calcination at elevated temperatures (500−750 °C) in air. XRD patterns showed that the amorphous phase of the nanopartic...