Sonochemical assisted synthesis of SrFe12O19 nanoparticles

•SrFe12O19 nanoparticles were prepared by a sonochemical assisted method.•The sonochemistry process was optimized in order to reduce the sonication time.•A synthesis mechanism during sono-assisted process is proposed.•The specific magnetization of the synthesized ferrites is in good agreement with widely published results.•Nanoparticles of hexaferrite obtained exhibit higher coercivity than similar reported. We present the synthesis of M-type strontium hexaferrite by sonochemistry and annealing. The effects of the sonication time and thermal energy on the crystal structure and magnetic properties of the obtained powders are presented. Strontium hexagonal ferrite (SrFe12O19) was successfully prepared by the ultrasonic cavitation (sonochemistry) of a complexed polyol solution of metallic acetates and diethylene glycol. The obtained materials were subsequently annealed at temperatures from 300 to 900°C. X-ray diffraction analysis shows that the sonochemical process yields an amorphous phase containing Fe3+, Fe2+ and Sr2+ ions. This amorphous phase transforms into an intermediate phase of maghemite (γ-Fe2O3) at 300°C. At 500°C, the intermediate species is converted to hematite (α-Fe2O3) by a topotactic transition. The final product of strontium hexaferrite (SrFe12O19) is generated at 800°C. The obtained strontium hexaferrite shows a magnetization of 62.3emu/g, which is consistent with pure hexaferrite obtained by other methods, and a coercivity of 6.25kOe, which is higher than expected for this hexaferrite. The powder morphology is composed of aggregates of rounded particles with an average particle size of 60nm.