Bi–Li–P co-substituted YIG microwave ferrites: Sintering characteristics and gyromagnetic properties

With the advancement of 5G technology, it has become possible to realize lightweight, integrated, and miniaturized microwave devices based on LTCC technology. In order to achieve the low-temperature sintering of a crucial substrate material, yttrium iron garnet (YIG), this study employed a solid-state reaction method with the design concept of full-site lattice activation to fabricate YIG ferrite ceramics with multiple ions (Bi3+-Li+-P5+) co-substitution. The results demonstrate that the Bi3+-Li+-P5+ co-substitution reduces the synthesis temperature of the garnet phase, enabling the low-temperature sintering of YIG ferrites at around 900 °C. Ferromagnetic resonance linewidth decomposition analysis reveals that as the substitution amount increases, the densification of the ferrites significantly rise due to lattice distortion, leading to a substantial narrowing in pore-induced linewidth (ΔHp), while the anisotropy-induced linewidth (ΔHa) remains nearly unchanged. As a result, the overall FMR linewidth of the material is greatly reduced. The sample exhibited optimal performance at a substitution amount of x = 0.04 (ρ = 5.5 g/cm3, 4πMS = 1720 Gauss, Tc = 305 °C, ΔH = 242 Oe).