Key step in the synthesis of ultrafine strontium ferrite powders (SrFe12O19) by sol-gel method

Submicron strontium hexaferrite (SrFe12O19) particles were synthesized using the sol-gel route. Magnetic properties and structure of strontium ferrite powders were studied at various ranges of calcination temperature (Tca) (750-900 °C), calcination time (3 min-2 h), Fe/Sr molar ratios (RM) (10.5-12), and pH (1-8). The resultant particles were investigated using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. At 750 °C, the Sr-M phase could be obtained for 3 min in air. However, single-phase Sr-M, which had stabilized magnetic properties, was obtained at Tca of 850 °C for 2 h. In solutions at pH 1, magnetic properties of the obtained sample at RM = 10.5 were found to be optimal with maximum saturation magnetization of 56 emu/g and intrinsic coercive force of 6.7 kOe.