Microwave magnetic and high dielectric properties of Ca²⁺-Sn⁴⁺ co-substituted BiIn-YIG ferrites for device application

The yttrium iron garnet (YIG) microwave ferrite is one of the key basis materials for device application. In this study, Ca²⁺-Sn⁴⁺ ions was chose to co-substitute Y³⁺-Fe³⁺ ions in YIG ferrite. Bi_0.4Y_2.6−xCa_xFe_4.8−xIn_0.2Sn_xO₁₂ (x = 0.0-0.25 with a step of 0.05, BiIn-YIG) ferrite materials were synthesized via solid state reaction method. The phase formation, microstructure, magnetic and dielectric properties of all samples were carried out and discussed detailed. X-ray diffraction (XRD) patterns showed that Ca-Sn co-substitution did not change the phase structure of YIG garget ferrites, and scanning electron microscope (SEM) results showed Ca-Sn promoted even grains growth. With Ca²⁺-Sn⁴⁺ content increase, bulk density (ρ), specific saturation magnetization (σ) and saturation magnetization (4πM_s) showed the same trend of first increase and then decrease. When x = 0.2, the maximum bulk density of sample was 5.332 g/cm³, specific saturation magnetization (σ) was 28.22 emu/g, and saturation magnetization (4πM_s) was 1891.35 Gs. The real part of dielectric permittivity (ε’) and the real part of magnetic permeability (µ’) increased with Ca²⁺-Sn⁴⁺ co-substitution. When x = 0.25, the value of ε’ was 17.03 (@10 MHz), and the value of µ’ was 181.3 (@1 MHz). At 9.56 GHz, ferromagnetic resonance linewidth (ΔH) of samples decreased first from 149.09 Oe (x = 0.00) to 100.46 Oe (x = 0.20), and then increased to 116.04 Oe (x = 0.25). Based on the performances of x = 0.20 sample, a high frequency microwave circulator was designed and optimized. The isolation loss and insertion loss of were less than − 20 dB in the 8.7–11.75 GHz frequency range, with a V_SWR of less than 1.22. meanwhile, the circulator had an insertion loss higher than − 0.5 dB and the relative bandwidth of 31%. The results proved the possible application of these materials in high frequency microwave devices.