Effects of Zr-substitution on microstructure and properties of YCaVIG ferrites

Y_2.6−xCa_0.4+xZr_xV_0.2Fe_4.8−xO₁₂ (Zr_x:YCaVIG) ferrite materials have been prepared by an oxide process. The phase formation and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The effects of Zr⁴⁺ substitution on phase compositions, sintering properties, microstructures and electromagnetic properties were investigated. The results indicate that all the sintered specimens with different Zr⁴⁺ contents show a single garnet structure. The addition of ZrO₂ can gradually increase the lattice constant, and lower the sintering temperature and the theoretical density. With the increase of Zr⁴⁺ content, the dielectric loss (tan δ_ε) and coercivity (H_c) decrease and then slightly increase, which is due to the variation of the microstructure. But the saturation magnetization (4πM_s) shows the opposite variation compared to the former two properties. However, the dielectric constant (ε_r) remains stable and remanence (B_r) monotonically declines. Finally, the specimen of Y_2.3Ca_0.7Zr_0.3V_0.2Fe_4.5O₁₂ sintered at 1350° possesses the optimum electromagnetic properties: ε_r=14.8, tan δ_ε=1.35×10⁻³, 4πM_s=1638 Gs, B_r=596 Gs, H_c=0.75 Oe and ΔH (ferromagnetic resonance linewidth)=66 Oe.