Synthesis and Properties of Single Domain Strontium Hexa-ferrite Ultrafine Powders via a Surfactant-Assisted Co-precipitation Method

A surfactant-assisted co-precipitation method with polyethylene glycol (PEG) or cetyltrimethylammonium bromide (CTAB) as the surfactant has been used to synthesize high-quality strontium hexa-ferrite (SrM ferrite) ultrafine powders, and the influences of the surfactants on the phase formation, particle sizes and morphologies as well as the magnetic properties of the synthesized powders have been investigated. The results indicated that single phase SrM ferrite ultrafine powders with uniform particle size ranging from 150 nm to 200 nm had been synthesized with the surfactant, PEG-400 of 10 wt.%. They were characterized by a fine magnetic property with their magnetization at 1.2 Tesla of a high value about 68.0 emu/g and their coercive force of 4625Oe. Compared to CTAB and PEG-6000, the non-ionic surfactant PEG-400 with the short molecular chain was easy to attach to the surfaces of the precipitated precursors without greatly changing the co-precipitating process, and good for the dispersion of the precursors, which resulted in more uniform particle size distribution.