A new strategy to fabricate YIG ferrite joint with novel magnetic Bi2O3-CoO-Fe2O3-B2O3 glass

A new low-temperature magnetic Bi2O3-CoO-Fe2O3-B2O3 (BCFB) glass was designed to acquire magnetic yttrium iron garnet (YIG/YIG) joint. This paper investigated the thermal behavior of BCFB glass and its wettability on YIG. The microstructural evolution, mechanical and electromagnetic properties of YIG/YIG joint were systematically studied. CoFe2O4 nuclei were gradually formed, growing up into nano-scale CoFe2O4 crystals in the glass seam. Meanwhile, some CoFe2O4 crystals grew up excessively by swallowing nano CoFe2O4, reaching microns. YBO3 reaction layer was formed and grew into YBO3 whiskers at the interface of YIG/glass with the brazing temperature increasing. The joint shear strength increased, reaching a maximum of 85.2 MPa at 775 °C under the collaborative reinforcement of well-integrated interface and glass-ceramic seam, then declined due to the aggravative reaction. The dielectric constant of YIG/YIG joints decreased with the brazing temperature increasing, varying from 18.5 to 16.6 at the frequency of 10 MHz. AFM/MFM and VSM analyses indicate that the glass seam performed magnetic property. The saturation magnetization of BCFB glass reached about 4.2 emu/g and 5.0 emu/g heat-treated at 750 °C and 775 °C, respectively, which could effectively enhance the magnetism of the glass seam.