多成分系無アルカリガラスの粘性特性と結晶化挙動

抄録

Critical cooling rate Q^* for glass formation was determined by means of DTA method for a non-alkali multicomponent system of 39.8SiO₂·10.1Al₂O₃·24.4CaO·12.6ZnO·11.1TiO₂·2.0B₂O₃mol% composition. Q^* was found to be 1.5×10^-2°C/sec. Viscosity of the system was measured by the beambending and the counter balancing method. The liquidus temperature T₁ of the system was determined by DTA method. From the viscosity and T₁ data, the Liquidus viscosity η₁ was obtained (logη₁/PaS=0.94). The Q^*-η₁ relationship of the non-alkali system was compared with those of alkali silicate and alkali borate systems.
It was found that the present non-alkali system has a critical cooling rate equivalent to 94SiO₂·6Li₂O, 75B₂O₃·25Li₂O or 85B₂O₃·15Na₂O glass. The fusion entropy ΔS_f was calculated from eq. (2) using the values of liquid parameters of the non-alkali system. It became apparent that the non-alkali system has a considerably high ΔS_f value compared with the alkali borate or alkali silicate system. This was regarded to indicate that the present system is composed of various polyhedra, including SiO₄, AlO₄ or TiO₄ tetrahedra, thus easing a glass formation of a SiO₂ poor melt.