Microstructure and properties of YIG ferrite joint brazed by Fe2O3-doped bismuth composite glass

Abstract

Bismuth composite glasses doped with Fe 2 O 3 nanoparticles were utilized to braze yttrium iron garnet (YIG) ferrite. The effect of Fe 2 O 3 doping on the thermal property and structure of the composite glasses was studied. The microstructure, mechanical and dielectric properties of YIG/YIG joint were systematically investigated as well. The Fe 2 O 3 doping promoted the crystallization of Bi 2 SiO 5 and the conversion of [BO 4 ] units to [BO 3 ] units. [BO 3 ]/[BO 4 ] in the glass matrix reacted with Y 3+ and Fe 3+ diffusing from YIG base material to form Fe 2 O 3 blocks and lamellar YBO 3 . The gray YBO 3 changed from lamellar phase to needle-like phase with the brazing temperature increasing. The concentration of Fe 3+ increased along with the dissolution of Fe 2 O 3 nanoparticles, resulting in the extensive formation of Fe 2 O 3 nuclei. Consequently, the amount of the Fe 2 O 3 blocks increased with the Fe 2 O 3 doping increasing. The shear strength could reach 68.4 MPa via the combined strengthening of block Fe 2 O 3 and gray YBO 3 phases. The dielectric constant of YIG/YIG joint decreased with the Fe 2 O 3 doping and brazing temperature increasing due to the growth of Fe 2 O 3 and YBO 3 phases. The dielectric loss tangent of the YIG/YIG joint was close to that of the original YIG material with the frequency increasing.