Structural, electrical, and impedance properties of Co and Sn doped Ba${}_{0.5}$Sr${}_{0.5}$Fe${}_{12-2x}$O${}_{19}$ hexaferrite ceramics (0 ≤ x ≤ 1) and their evaluation for antenna application

The effect of doping of Co${}^{2+}$ and Sn${}^{4+}$ in Ba${}_{0.5}$Sr${}_{0.5}$Fe${}_{12-2x}$O${}_{19}$ hexaferrite with different concentrations (x = 0.2, 0.4, 0.6, 0.8, and 1.0) was studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), complex impedance spectroscopy, and analyzed as a dielectric resonating antenna (DRA) at room temperature. The samples were produced and sintered by the solid-state reaction method. Their structure appeared from the M-phase type while their increase in grain size evidenced a dependency on Co-Sn content. The dielectric constant and loss tangent, inferred from impedance spectroscopy, also decreased with the corresponding increase in doping. The real and imaginary impedance decreased with the frequency increment. An electrical equivalent circuit using the Resistance-Constant Phase Element (R-CPE) association was thus proposed, the best-simulated components fitting with the observed structural and microstructure properties. It enabled a better understanding of the microstructure through simulated values of grain/grain boundaries and its effect on tuning the electrical properties in the low-frequency regime. The ferrite characteristics were tested for dielectric resonator antenna applications owing to their good inherent behavior than microstrip patch antenna. Measurement of the radiation efficiency, gain and bandwidth parameters of all the produced ceramics showed that the non-doped one (x = 0.0) exhibits the optimum values: 99.91%, 4.24, and 2.89 GHz, respectively, making the most valuable for antenna applications.