Joining MgAl2O4 ceramics using ZnO–Al2O3–SiO2 glass ceramic with precipitated ZnAl2O4

Abstract

In this work, crystallization, thermal expansion and wetting behavior of ZnO–Al2O3–SiO2 (ZAS) glass were first investigated. The results showed that ZnAl2O4 was precipitated from ZAS glass after crystallization treatment. Crystallization increased the coefficient of thermal expansion (CTE) of ZAS glass ceramic due to the high CTE of ZnAl2O4. In addition, ZAS glass exhibited good wettability on the surface of MgAl2O4 substrate. On this basis, ZAS glass was used to join MgAl2O4 ceramic, and the microstructure and mechanical properties of joints obtained with different cooling methods were investigated. The flexural strength of joints was related to the content of ZnAl2O4 crystals in the brazing seams. Additional nucleation and crystallization treatment during cooling process improved the crystallinity of brazing seam, resulting in better matching of the CTE of brazing seam with that of MgAl2O4 ceramic. The maximum flexural strength of joints reached 201 MPa, which was equivalent to the strength of MgAl2O4 ceramic.