A new design of the YIG/MTC joint brazed by bismuth-based glass

The paper uncovers an underlined mechanism of joining Yttrium Iron Garnet (YIG) and Magnesium Titanate Ceramic (MTC) with a bismuth-based glass braze. The proposed joint design has not been investigated until present. The central hypothesis is as follows. The brazed bismuth-based glass microstructure and the resulting mechanical strength of a YIG/MTC joint design support favorably a good bonding of the interface domains. The supporting evidence includes the following: (i) the bismuth-based glass features good wettability on YIG and MTC, (ii) the sequence of the coefficients of thermal expansions (YIG, bismuth-based glass, MTC) is in a favorable succession. The study reveals that the interface reactions form: (i) a lamellar phase and YBO₃ whiskers at the YIG/Bi25 interface, (ii) both MgFe₂O₄, and Bi₄Ti₃O₁₂ whiskers in addition to Zn₂Ti₃O₈ reaction layer at the MTC/Bi25 interface, and (iii) Fe₂O₃ phase along the brazing seam. The mechanical integrity of joints has been studied as well.