| Abstract
| - This article describes the synthesis of barium ferrite nanoparticles at low crystallization temperatures usinga sodium citrate-aided process. Monodispersed barium ferrite amorphous nanoparticles were synthesized bythe formation of metal−citrate complexes at pH 10, followed by hydrolysis at 100 °C. The mean particlediameter was 4.7 nm with a specific surface area of 137.8 m2/g. This is the first time that sodium citrate hasbeen used as a chelating agent in the synthesis of barium ferrite nanoparticles. Sodium citrate plays twoimportant roles in the process: it allows the homogeneous mixing of two metal cations in the as-synthesizedbarium ferrite amorphous nanoparticles, and it retards particle growth via the formation of surface citratecomplexes, inhibiting the agglomeration of the nanoparticles. The amorphous precursor nanoparticles weretransformed into a hexagonal structure by calcination at elevated temperatures (500−750 °C) in air. XRDpatterns showed that the amorphous phase of the nanoparticles was completely transformed to the hexagonalphase after calcination at 600 °C for 100 min, with no intermediate phase evident. This crystallizationtemperature was lower than previously reported crystallization temperatures. Crystallization behavior wasexamined using thermal analysis and FTIR measurements. Particle size, measured from SEM images, wasincreased from 35 to 130 nm by elevating the calcination temperature from 600 to 750 °C. Barium ferritenanoparticles calcinated at 600 °C had high magnetic properties: the coercivity and saturation magnetizationvalues were 3580 Oe and 43 emu/g, respectively.
|
