Primary and secondary phase separation of sodium silicate glasses

doi:10.1016/0022-3093(68)90004-5

Journal of Non-Crystalline Solids

Volume 1, Issue 1, December 1968, Pages 29-38

https://doi.org/10.1016/0022-3093(68)90004-5 Get rights and content

Abstract

The immiscibility curve in the system Na₂OSiO₂ shows that the amount of Na₂O content in the silica rich phase is small at 500°C and hardly changes with temperature up to 800°C but increases sharply in the interval 800–865°C. The silica content of the alkali-rich phase increases continuously with temperature. The curve is thus extremely asymmetric. The electron microscope photographs show that the separate phases (primary phase separation) separate again into two phases during cooling or during a second heating of the glass at a lower temperature. This secondary phase separation does not depend upon the duration of the initial heating of the glass. It is connected with the asymmetry of the immiscibility curve. The alkali-rich phase separates more easily but with the help of a repeated treatment the silica-rich phase can also be caused to phase separate. This secondary phase separation is a general phenomenon and must be given attention when discussing the number of phases in the glass. Certainly the existence of triple-phase glasses cannot be excluded. Phase separation of higher orders can be achieved with the help of heat treatments in several steps.

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Primary and secondary phase separation of sodium silicate glasses

Abstract

Critical phenomena in sodium silicate glasses

A study of the supermolecular structure of silicate glasses by direct methods

Some aspects of the formation of new phases in melt and glasses

Dokl. Akad. Nauk SSSR

Physics of Non-Crystalline Solids

Electron microscope investigation of the heterogeneous structure and initial crystallization stages of glasses in the system Li2OSiO2

Verres et Refractaires

Dokl. Akad. Nauk SSSR

Electron microscope investigation of the heterogeneous structure and initial crystallization stages of glasses in the system Li₂OSiO₂