Study on Bi3+-Al3+ co-doped YIG for co-firing YIG-Al0.2/NZF ferrite composite substrates

Abstract

Y2.5-xBi0.5AlxFe5O12 (YIG-Alx) ceramics have been synthesized at 1175 ℃ by the solid-state reaction method. The effects of the co-doped Bi3+, Al3+ ions on the phases, micromorphology, and dielectric and magnetic properties of the yttrium iron garnets (YIG) were investigated. Excessive introduction of Al3+ ions led to the collapse of the YIG lattice and precipitation of the Bi3+ and Fe3+ ions; while moderate Al3+ doping improved the dielectric properties, but not the saturation magnetization. The YIG-Al0.2 ceramics proved to have particularly good electromagnetic properties (εr = 18.34 ± 0.05@11.19 GHz, tanδ = 3.09 ± 0.55 × 10−4, Ms = 19.82 ± 0.55 emu/g). Additionally, tightly bonded Y2.3Bi0.5Al0.2Fe5O12/Ni0.8Zn0.2Fe2O4 (YIG-Al0.2/NZF) composite substrates were prepared by co-firing at 1175 ℃. The composite substrates exhibited superior electromagnetic properties (YIG-Al0.2: εr = 18.37 ± 0.05@11.15 GHz, tanδ = 3.08 ± 0.55 × 10−4, Ms = 21.09 ± 0.55 emu/g; NZF: Ms = 67.5 ± 0.55 emu/g), which were slightly affected by the diffusion of Ni and Zn from the NZF. Our findings show that YIG-Al0.2/NZF substrates have great potential for use as RF band circulators.