Interfacial evolution mechanism of MgAl2O4/MgAl2O4 joints bonded with lanthanum glass

The La2O3-SiO2-B2O3 (LSB) glass filler with high softening temperature was first used to join MgAl2O4 ceramic. An interfacial layer composed of Al2O3 was formed due to the solubility difference of MgO and Al2O3 in the LSB glass filler. As a result, the addition of Al2O3 into the LSB glass filler caused the increase of interfacial layer thickness. On the contrary, the addition of MgO into the LSB glass filler led to the decrease of interfacial layer thickness. When the adding content of MgO was 6 wt%, the interfacial layer disappeared and completely amorphous brazing seam was obtained. The in-line transmittance of joints decreased with the increase of the thickness of interfacial layer. The optimal in-line transmittance of joint bonded with La2O3-SiO2-B2O3-MgO (LSB6M) glass filler reached 82.9% at 1000 nm. Meanwhile, the average flexural strength of joints was about 196.2 MPa, which was equal to the strength of MgAl2O4 substrate.