Magnetic and dielectric composite powders from BaM-ferrite and BaTiO3 were fabricated by a high-energy milling process and subsequent annealing. It is shown that the BaTiO3 phase dominated after high-energy milling for 40 h with increasing BaTiO3 content up to 20 wt.%. On the other hand, the BaFe12O19 phase dominated after annealing the mixed sample at 900 degrees C for 3 h in air. The lattice constant of the c-axis for the high-energy milled sample increased with BaTiO3 content, but the BaFe12O19 phase was formed as a stable structure after annealing and little change was seen with BaTiO3 content. From the HR-TEM micrographs, partial mismatch in orientation was observed in 10 nm nanosized microstructures. It is also shown that magnetic hysteresis loops for the mixed powder of BaFe12O19/BaTiO3 were affected by the properties of the BaFe12O19 matrix with a rather large spacing in the c-axis direction. A narrowed hysteresis loop. was formed after the high-energy milling process because of the mechanical stress-induced magnetic structural deformation and modified domain structure by the high-energy milling process. The stable hard ferrite BaFe12O19 Structure can be achieved after annealing at 900 degrees C through the rearrangement of atoms. The microwave absorbing property was enhanced from the composite powder of BaFe12O19/BaTiO3 obtained by the mechanical milling. The reflection loss of the BaFe12O19/BaTiO3 Composite was over -25 dB at 16.5 GHz and about -15.3 dB for only the barium ferrite (BaFe12O19).

Keywords: barium ferrite composite; high-energy milling; microwave absorber