Preparation and magnetic properties of barium hexaferrite nanoparticles prepared by sol-gel method

Barium hexaferrite powders have been prepared using a sol-gel process under the different pH values and the different calcined temperatures. The influence of the pH value and the calcined temperature on the crystalline structure and the magnetic properties of barium hexaferrite were studied by XRD, FSEM and VSM. The experimental results show that the pH value of sol solution and the calcined temperature can obviously affect the crystalline structure and the magnetic properties of the as-prepared barium hexaferrite. It is positive for the formation of BaFe12O19 phase when pH value is above 3, the saturation magnetization M-s and coercivity H-c of the as-prepared barium hexaferrite nanoparticles with the uniform size of about 50 nm reach maximum at pH=7. Furthermore, the BaFe12O19 began to form at 700 degrees C with other phases such as alpha-Fe2O3, BaFe2O4 and BaCO3, with the increasing of the calcined temperature. The formation of BaFe12O19 phase went on, and finally the sample was pure BaFe12O19 phase when the calcined temperature arrived at 800 degrees C. The barium hexaferrite sample calcined at 900 degrees C with the solution pH value of 7 exhibited the best magnetic properties: the saturation 2 magnetization M-s = 61.6 (A.m(2))/kg and the coercivity H-c = 4.56 X 10(5)A/m.