Crystallization behavior during cooling and glass-forming ability of Al2O3-poor Li2O-Al2O3-SiO2 melts

The influence of K2O/(MgO + K2O) on some melt properties, including crystallization during cooling of melts and glass-forming ability, was investigated in the Li2O-Al2O3-SiO2 system with low Al2O3 content. The dependence of viscosity on K2O/(MgO + K2O) above 1000 °C showed a monotonic decrease due to the reduction of [MgO4] concentration and the conductivity also decreased due to the larger ion radius of K. The temperature dependence of conductivity for all melts showed an abrupt change at one temperature due to crystallization in which temperature of crystallization decreases with increase of K2O. The crystallization behavior near liquidus temperature was studied quantitatively by calculating the crystal volume fraction from apparent viscosity value. The glass-forming ability of the melts was discussed by using data related with viscosity and crystallization. Finally, it was suggested that the melts with K2O/(MgO + K2O) ⩾ 0.75 have a good glass-forming ability.