SINTERING-VISCOSITY RELATION FOR MIXED-ALKALI GLASS POWDER COMPACTS

The sintering of glass powder compacts was studied by dilatometer in the (25 - x) Na2O-xK(2)O-75SiO(2) glass system. The dilatometrically determined sintering temperature (T-sin) at constant heating rate decreases and the shrinkage at isothermal sintering increases when Na2O is replaced by K2O up to the mole fraction of K2O/(Na2O + K2O) = 0.5. This is due to the decrease in viscosity and means that sintering can be possibly accelerated by introduction of mixed alkali oxides in this system, According to calculation using the VFT-equation, the viscosity value at T-sin is almost independent of glass composition, From these results it may be supposed that the dilatometrically determined sintering begin temperature (T-sin) can be a characteristic point for the sintering of glass.