Studies in Germanium Oxide Systems: II, Phase Equilibria in the System Na ₂ O—GeO ₂

Abstract

Phase equilibrium relations in the system Na 2 O‐GeO 2 have been determined using standard quenching techniques supplemented by differential thermal analysis. Two congruently melting compounds, Na 2 O·GeO 2 and 2Na 2 O·9GeO 2 , exist; the melting points are 1103°± 15°C and 1073°± 3°C, respectively. The eutectic temperature between GeO 2 and 2Na 2 O·9GeO 2 is 950°±f 10°C at 94.5 wt GeO 2 . The eutectic temperature between 2Na 2 O · 9GeO 2 and Na 2 O·GeO 2 is 790° f 10°C at about 75 wt% GeO 2 . Both the refractive index and the density of glasses in the system Na 2 O‐GeO 2 exhibit maximum values at about 16 to 18 mole % Na 2 O. The Ge‐O‐Ge absorption band at 890 cm −1 shifts toward lower wave numbers with the addition of Na 2 O.