Enhanced magnetodielectric properties of Co2Z ferrite ceramics for ultrahigh frequency applications achieved via Cr3+ ion doping

Phase formation, microstructure, magnetic properties, and dielectric properties of Ba1.5Sr1.5Co2Fe(23−x)CrxO41 (0.0 ≤ x ≤ 1.0) ceramics, in which Fe3+ ions were substituted by Cr3+ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr3+ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr3+ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm3. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr3+ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices.