Dielectric Properties of BaFe₁₂O₁₉ Doped with SiO₂ in the Low Frequency Region

A submicron powder of barium hexaferrite BaFe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</inf> doped with SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was pressed at 0.2 GPa in thin discs and sintered for 2 hours at temperatures in the range of $1050^{\circ} \mathrm{C}$ to $1275^{\circ} \mathrm{C}$ in the air. The sintered disk samples were covered on both sides with Ag silver epoxy and dried in air for 30 min. Two small, disk-shaped electrodes, made of brass, were used to form a disk adapter for measuring the capacitance and resistance of sintered samples in the very low-frequency region. A chemical impedance analyzer, Hioki IM 3590, was used to measure capacitance and resistance for a serial and parallel model of the equivalent circuit as a function of frequency in the range from 0.1 Hz to 100 kHz. The modulus of colossal dielectric permittivity $\varepsilon_{\mathrm{r}}$ was determined from the model of a disk capacitor and compared with the pure barium hexaferrite value and previous results. The dissipation factor $\operatorname{tg} \delta$ was also calculated from the measured values of resistance and capacitance. The obtained values were compared with the best literature results.