Reducing the grain gap and improving the saturation magnetization of co-fired YIG-Al0.1/NZF-Zn0.4 ferrite composite substrates with an ASBP-glass sintering aid

Abstract

Ni0.6Zn0.4Fe2O4 (NZF-Zn0.4) ferrites with different Al–Si–B–Pb (ASBP) glass additions were synthesized via a solid-phase reaction method at 1175 °C. The inclusion of ASBP-glass significantly enhances the grain size, density, shrinkage, and magnetic properties of NZF-Zn0.4 ferrites without introducing impurity phases. The prepared NZF-Zn0.4-1 wt%ASBP ferrites not only exhibit appropriate radial shrinkage but also possess a dense microstructure and outstanding magnetic properties. Subsequently, Y2.4Bi0.5Al0.1Fe3O4 (YIG-Al0.1) ferrites and NZF-Zn0.4-1 wt%ASBP ferrites were chosen as the outer rings and inner cores, respectively. Tightly interconnected YIG-Al0.1/NZF-Zn0.4–1wt.% ASBP ferrite composite substrates were successfully co-fired within the temperature range of 1175 °C–1225 °C following co-pressing. Furthermore, YIG-Al0.1/NZF-Zn0.4-1 wt%ASBP composite substrates, co-fired at 1175 °C, exhibit a lack of impurity phases in the interface region, minimal element diffusion, and exceptional electromagnetic properties (NZF-Zn0.4-1 wt%ASBP: Ms = 81.88 ± 0.05 emu/g; YIG-Al0.1: εr = 18.28 ± 0.05@11.17 GHz, tanδ = 3.14 ± 0.55 × 10−4, Ms = 21.62 ± 0.55 emu/g). The wide co-firing temperature range of YIG-Al0.1/NZF-Zn0.4-1 wt%ASBP composite substrates significantly enhances the shrinkage matching rate of two-phase ferrites, and its exceptional electromagnetic properties hold significant potential for applications in RF band circulators.