ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

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


PHASE RELATIONS IN THE SILICA RICH AREA OF THE SYSTEM Li₂O-SnO₂-SiO₂
 
Štemprok Miroslav 1, Voldán Jan 2
 
1 Ústřední ústav geologický, Malostranské náměstí 19, 118 21 Praha 1
2 Státní výzkumný ústav sklářský, Škroupova 957, 501 92 Hradec Králové

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.


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