Immiscibility, nucleation and crystal growth in the soda-baria-silica system

The regions of glass formation and liquid-liquid immiscibility have been determined in the soda-baria-silica system. Immiscibility occurs in the high silica corner of the system, and extends over a continuous region from the BaO—SiO2 to the Na2O—SiO2 limiting binaries. In an extensive region close to the glass-forming boundary and including mostly the barium disilicate field, crystallization occurred by homogeneous nucleation to produce a glass ceramic. Some of these compositions also showed metastable immiscibility. Nucleation, growth and coarsening of the crystals were studied; first, a metastable high-temperature polymorph of barium disilicate appears growing as spherulites, but on prolonged heating a lathe-like structure appears.