Ceramics-Silikáty 31, (1) 1 - 16 (1987)

The glasses of the composition Li₂O.nSiO₂ (where n = 2, 3, 4, 5 and 6) with the additions of the amount of SnO₂ up to 30 % were melted in air at 1500-1600 °C. Their crystallization was studied by the gradient method in ceramic boats and by the quenching method. The liquidus surface of the portion of the diagram Li₂O-SnO₂-SiO₂ tested is characterized by the fields of primary crystallization of cassiterite, tridymite, lithium metasilicate and lithium disilicate. A ternary eutectic point was found at the temperature 965 °C. Glasses exhibit metastable liquid immiscibility which decreases with the raising amount of SnO₂. Our results and the comparison with the system Na₂O-SiO₂-SnO₂ suggests that SnO₂ belongs to network formers and it is copolymerized with silica tetrahedra in the silicate network. The subsolidus part of the system showed at 880 °C the phase of brennockite Li₄Sn₂Si₁₂O₃₀ which is formed in high silica runs extremely slowly.