Synthesis and magnetic properties of strontium hexaferrite from celestite ore

Nanocrystalline strontium hexaferrite (SrFe12O19) powders have been synthesized from Egyptian celestite ore (SrSO4), as a source of strontium, via co-precipitation route. The raw celestite ore was first dissolved in hydrochloric acid to remove about 10% CaO and the acid soluble impurities associated with the ore. Then, the treated celestite was washed and dried followed by a reduction with carbon to give acid–water soluble strontium sulfide SrS. The ferrite precursors were obtained from a precipitation of the produced SrS dissolved in dil. HCl and pure ferric chloride at pH 10 using 5 M sodium hydroxide. These precursors were annealed at 1000 °C for constant time 2 h in open atmosphere. The effect of Fe3+/Sr2+ mole ratio on the formation, crystallite size, morphology and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and VSM, respectively. The results obtained showed that the single phase SrFe12O19 powders was achieved at the Fe3+/Sr2+ mole ratios 8.57 and 8.00 at annealing temperature 1000 °C for 2 h. The maximum saturation magnetization (74.15 emu/g) was achieved at the Fe3+/Sr2+ mole ratio to 8.57 and annealing temperature 1000 °C due to the formation of a uniform-like hexagonal shape structure. Moreover, wide coercivities can be obtained at different synthesis conditions (2011–3504 Oe).