Influence of Ca Ions on Surfactant Directed Nucleation and Growth of Nano Structured Iron Oxides and Their Magnetic Properties

We report a combination of a surfactant-directed approach and calcium ion incorporation during synthesis of nano iron oxide/oxyhydroxide that will result in selective phase formation of goethite (alpha-FeOOH) nanorods and pseudocubic hematite in aqueous solution using a simple coprecipitation method. The calcium content was varied from nil to 2.25%. The prepared samples were characterized by XRD, raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At low concentration of calcium, acicular goethite particles formed the predominate phase, while, with Ca concentration of 2.25%, monodispersed pseudocubic hematite partides were the major phase. Mossbauer spectroscopy has been successfully used to detect the iron containing oxide/hydroxide phases, some of which could not be detected by XRD. The local environment of the iron atoms of these phases has also been detected by this technique. Room temperature magnetization measurements using a vibrating sample magnetometer (VSM) show variation of magnetic properties as a function of doping concentration of Ca(2+) in these materials with different size and morphology.