Nano-sized powders of SrFe₁₂O₁₉ synthesized by the sol-gel method

By means of inorganic salt precursor of strontium nitrate and ferric nitrate, the sol was confected by non-stoichiometry and the citric acid sol-gel method was used to prepare Sr-ferrite nanoparticles. The Sr-ferrites were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and filed-emission scanning electronic microscope (FESEM). The development process, forming mechanism and the magnetic properties with temperature of Sr-ferrite were analyzed. The results show that the annealing of gels by 'two steps' method decreased non-magnetic material and declined the Sr-ferrite temperature of forming singleness. The Sr-ferrite forms at the temperature of 600-700°C and the singleness is acquired at the temperature of 900°C, the Sr-ferrite growth is consistent of the variety of magnetic properties. The maximum coercivity value was gained at 800°C, the coercivity value (H_c) and the specific saturation magnetization value (σ_s) is 454.16 kA/m, 55.91 A · m²/kg.