Compressibility of magnesium silicate glasses in comparison with those of aluminosilicate glasses

• Refractive index and the compressibility of Na2MgSi6O14 glass are measured.
• Degree of depolymerization is calculated according to the method proposed in the work.
• Compressibilities of Mg- and Al-silicate glasses too are not differed from each other.
• Obtainedresults showed that Mg2+ mainly act as network formers in silicate glasses.
• Compressibility of glasses can be predicted from its degree of depolymerization.

The refractive index of the Na2MgSi6O14 glass in the pressure range up to 6.0 GPa has been measured using a polarization-interference microscope and an apparatus with diamond anvils. The changes in relative density which characterize the compressibility of the glass have been estimated in the pressure range under investigation from the measured refractive indices within the framework of the theory of photoelasticity. The results have been compared with the data previously obtained for the NaAlSi3O8 and CaAl2Si6O16 glasses. A comparison of the changes in relative density of the aluminosilicate and magnesium silicate glasses has been demonstrated that the difference in the compressibility is not so much significant as should be expected from the replacement of network-forming ions by modifiers ions. Estimated by different methods the degree of depolymerization of the Na2MgSi6O14 glass (NBO/T ≅ 0.2) is compared to those for the aluminosilicate glasses. The decrease in the compressibility in the series NaAlSi3O8, CaAl2Si6O16, Na2MgSi6O14 glasses is in agreement with an increase of the degree of depolymerization in the same series.

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