Characterization and magnetic properties of BaxSr1−xFe12O19 (x = 0–1) ferrite hollow fibers via gel-precursor transformation process

The BaxSr1−xFe12O19 (x = 0–1) ferrite hollow fibers with diameters of 1 to 2 μm have been prepared by the gel-precursor transformation process. The gel-precursor decomposition and ferrite formation were analyzed by thermo-gravimetric and differential scanning calorimetry, infrared spectroscopy and X-ray diffraction. The BaxSr1−xFe12O19 ferrite hollow fibers as-prepared were characterized with scanning electron microscopy and vibrating sample magnetometer. The results show that the BaxSr1−xFe12O19 (x = 0–1) ferrite hollow fibers are of a solid solution and these fibers with an obvious hollow structure consist of fine hexagonal plate-like particles. Their magnetic properties are mainly influenced by the chemical composition and grain size. With the barium substitution, the specific saturation magnetization and coercivity of the BaxSr1−xFe12O19 ferrite hollow fibers decrease from 67.1 Am2/kg and 443.3 kA/m (for the simple SrFe12O19 ferrite, x = 0) to 56.1 A m2/kg and 319.8 kA/m (for the simple BaFe12O19 ferrite, x = 1.0), respectively. The Ba0.5Sr0.5Fe12O19 ferrite hollow fibers calcined at 1000 °C for 2 h are composed of single-domain grains around 60 nm and exhibit the specific saturation magnetization 63.9 A m2/kg and coercivity 416.5 kA/m.

Research highlights▶ The BaxSr1−xFe12O19 (x = 0–1) ferrite hollow fibers with diameters 1–2 μm have been successfully prepared by the gel-precursor transformation method for the first time. ▶ The BaxSr1−xFe12O19 ferrites hollow fibers have an obvious hollow structure and the ratio of the hollow diameter to the fiber diameter estimated about 1/2. ▶ With the barium substitution, the Ms and Hc of the BaxSr1−xFe12O19 ferrite hollow fibers decrease due to the super-exchange interaction.