Effect of MgO addition on crystallization and properties of Li2O-ZnO-SiO2 glass-ceramics seals for copper

The properties of Li2O-ZnO-SiO2 (LZS) glass-ceramics with addition of 6 mol% MgO were investigated. With MgO addition, the glass transition temperature (T-g) and the crystallization temperature (T-c1. T-c2) all decreased. There were more cristobalite and Li3Zn0.5SiO4 phases in the MgO-doped samples, according to the XRD analysis. The results of crystallization kinetics showed LZS with MgO addition has lower activation energy (E) and higher crystallization index (n) and reaction rate constant (k), indicating MgO in LZS system can promote crystallization. The microstructures also showed the MgO-doped glasses had higher crystallinity and larger grain size. The sample hardness with MgO addition was higher. The average thermal expansion coefficient (a) of the MgO-doped glass-ceramics in the temperature range 20-400 degrees C was from 153.2 x 10(-7) K-1 to 179.0 x 10(-7) K-1, and it was lower than that of MgO-free glasses. MgO in LZS could make it more suitable for sealing with copper (alpha =177 x 10(-7) K-1). (C) 2014 Elsevier B.V. All rights reserved.