Lithium zinc silicate (LZS) glasses containing Li2O–ZnO–SiO2–Na2O–B2O3–P2O5 were prepared by conventional melt and quench
technique and subsequently converted to glass-ceramics by controlled nucleation and crystallization. Both these parameters were determined
by differential thermal analysis (DTA) studies. The effect of ZnO/(ZnO+SiO2) ratio on various thermo-physical properties was investigated
by changing the ratio from 0.1 to 0.31. A number of crystalline phases have been identified by X-ray diffraction studies on the glass-ceramics
including cristobalite (SiO2), lithium zinc silicate (Li3Zn0.5SiO4) and lithium silicate (Li2SiO3). Density (q) was found to increase from 2.62
to 2.82 g cm3 while microhardness (Vicker’s hardness number, VHN) decreased from 6.56 to 5.79 GPa with increase in ZnO/(ZnO+SiO2)
ratio in the glass-ceramics. Average thermal expansion coefficient (TEC) in the temperature range 30–450 jC increased from 125107 to
185107/jC. The increase in expansion coefficient and decrease in microhardness are thought to be due to the formation of different phases
which in turn influence the rigidity/bonding in the glass-ceramics. The material has been used for the fabrication of hermetic seal with copper.
A study on the microstructure close to the interface of the glass-ceramics to metal is also carried out. The seal withstands a vacuum off106
Torr at helium leak rate of 31010 Torr l/s.