Abstract:

FeCl3 and NaOH were used as raw material and precipitator respectively to prepare a spherical Fe(OH)3 intermediate by chemical precipitation. FeCl2 and other precipitators (Na2CO3, NH3·H2O and NaOH) were also used to prepare shape-controlled intermediates via co-precipitation. The intermediates were then covered with a citric acid and Sr complex by the citrate acid method. Spherical, spindly and rod-like nano-SrFe12O19 particles were obtained after calcination of the covered precursors. The shape-controlled nano-SrFe12O19 particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the magnetic properties of the samples were studied using a vibrating sample magnetometer (VSM). Results showed that the type of ferric salt and the alkalinity of the precipitator greatly influenced the phase of the intermediate and the morphology of the SrFe12O19 particles. Spherical nano-SrFe12O19 particles were obtained when Fe3 + was used as a raw material, and shape-controlled nano-SrFe12O19 particles were obtained when Fe2+ was used as a raw material together with precipitators of different alkalinity. The slenderness ratio and shape-anisotropy of the samples increase as the alkalinity of the precipitator increases. The coercivity (Hc) of SrFe12O19 is mainly dependent on the anisotropy of the particle. The coercivity and the saturation magnetization (Ms) of SrFe12O19 increase as the anisotropy of the samples increases. The coercivity and the Ms of the rod-like SrFe12O19 particles obtained using FeCl2 and NaOH were optimal 458.2 kA·m-1 and 64.2 A·m2·kg-1, respectively.

Key words: Shape-controlled, Nano-SrFe12O19, Chemical precipitation-citric acid method, Magnetic property