Effect of Reaction Time on the Coercivity of Barium Ferrite Synthesized by Hydrothermal Process

The barium ferrite BaFe12O19 with c-plane anisotropy, which possessed relative high saturation magnetization and low coercivity, had been synthesized by hydrothermal method with different reaction time of 5 h, 8 h,11 h,14 h, and 17 h. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to study the phase composition, microstructure and magnetic properties of barium ferrite, respectively. The results showed the intensities of the peak were enhanced and there was no impurity phase. With the prolonging of the reaction time to 11 h, 14 h and 17 h, the grain size increased, and the equivalent diameter was about 1 μm, and the thickness was about 100 nm. When the reaction time was 17 h，the coercivity of barium ferrite was 1104 Oe. The reduction of coercivity was ascribed to the increase of particle size and the reduction in magnetic anisotropy.