Colossal permittivity of sintered BaFe12O19 doped with SiO2 in the very low frequency region

Barium hexaferrite BaFe12O19 composition was prepared using the respective powder mixture of metal oxides BaCO3 : 6?Fe2O3 and by performing a solid-state reaction at 1000?C/4h in air. The obtained barium hexaferrite was milled for a prolonged time in the planetary ball mill and agate mill to achieve a fine powder of submicron particle size. The prepared powder was characterized using XRD and SEM techniques.The BaFe12O19 submicron powder was mixed with 2.5 % wt. SiO2 nanopowder as a dopant. After that, the doped barium hexaferrite powder mixture was pressed into small and thin disk samples at 0.2 GPa. The prepared disk samples were sintered at different sintering profiles from 1050?C to 1275?C/2h in air. The sintered samples were also characterized using XRD and SEM. The main electrical properties such as disk capacitance C and resistance R at 1Hz to 100 Hz were measured using a low frequency impedance analyzer. The dielectric permittivity ?r and dissipation factor tg? were calculated from the equivalent disk capacitor electrical schemes. The obtained results were used for observing space charge relaxation effects and colossal permittivity.