THERMAL-EXPANSION OF LI2O-ZNO-AL2O3-SIO2 GLASSES AND CORRESPONDING GLASS-CERAMICS

The thermal expansion behaviour of some glasses and glass-ceramics within the system Li2ZnSiO4-LiAlSi2O6 is described. The effect of TiO2 and ZrO2 additions is also evaluated. The expansion coefficient (alpha) of the glasses increases with an increase of the Li2ZnSiO4 component in the glass composition. TiO2 and ZrO2 were found to decrease the thermal expansion of the glasses investigated. The dilatometric transition and softening points of the glasses showed the reverse behaviour. The thermal expansion of the glass-ceramics exhibited a wide range, depending upon the type and relative proportions of the crystalline phases present. The alpha-values of the glasses ranged between 73.6 and 97.4 x 10(-7)-degrees-C-1 in the temperature range 20-450-degrees-C and those for the crystalline products ranged from 36.1 and 102.6 x 10(-7) in the temperature range 20-450-degrees-C.