Ca-Ge co-substituted BiZr-Y3Fe5O12 ferrite with high dielectric constant and low loss for miniaturized microwave device application

Yttrium iron garnet (Y3Fe5O12, YIG) ferrite has excellent dielectric and magnetic properties, and is widely used in microwave communication devices. In recent years, to meet the demands of integration and miniaturization, it is necessary to increase the dielectric constant of YIG while maintaining a low ferromagnetic resonance (FMR) linewidth. In this study, high-dielectric ferrite materials with the formula Y1.85-xBiCa0.15+xFe4.85-xZr0.15GexO12 (x = 0.0–0.6 with a step of 0.1) were prepared by the solid-state reaction method. The effects of Ca-Ge co-substitution on the phase formation, microstructure, dielectric and magnetic properties of BiZr-YIG materials were investigated by X-ray diffraction, scanning electron microscopy, impedance analyzer, vibrating sample magnetometer, and FMR linewidth systems. The results indicate that Ca-Ge substitution reduced the saturation magnetization from 1535.53 G (x = 0.0) to 480.58 G (x = 0.6). When x = 0.2, the material exhibited a high dielectric constant (ε' = 22.20 @20 MHz), low dielectric loss (tanδε =5.54×10−3 @20 MHz) and a narrow FMR linewidth (254.31 Oe). This study shows that appropriate Ca-Ge ion substitution could effectively improve dielectric properties, and reduce dielectric loss and FMR linewidth. The high dielectric constant of this material lays a foundation for the miniaturization of microwave devices.