Phase diagrams and sinter aids (Cs2O) for SiO2-Sinterglass

Abstract

Considering sintering as the technology of choice even for amorphous glasses [1-5], viscous flow has to be taken into account as the transport mechanism instead of diffusion [6-9]. In this context viscosity provides a new fix point among others (Fig. 1): the minimum sintering temperature [10]. This temperature should change in a definite way if twocomponent glass systems such as caesium silicate glasses are considered. If caesium oxide is assumed to be most compatible with amorphous silica, forming a homogeneous liquid and solid solution (glass) at different concentrations, then the minimum sintering temperature for single-phased glasses should decrease with increasing Cs20 content according to decreasing viscosity. If, however, the amorphous Cs20-containing silica latently reflects the constitutional phase relations according to the eutectic phase diagram for crystalline silica and caesium oxide, then the minimum sintering temperature for amorphous silica should be reduced for any addition of caesium oxide to an approximately constant temperature near or below the eutectic temperature for crystalline silica containing caesium oxide. Since the latter case was recently found for rubidium silicate glasses, and since it was possible in the same theoretical way as for the SiO2-Rb20 phase diagram [11] to prove the phase diagram for crystalline silica with caesium oxide to be reliable, four glasses of composition xCs20 + (100 x)SiO2, with x = 0, 6, 10 and 14mo1%, and one quartz crystal powder were examined in this study. For x = 0 (pure Si02 glass) a ready-made amorphous