Studies in Germanium Oxide Systems: I, Phase Equilibria in the System Li2O—GeO2

Phase equilibrium relations in the system Li₂O-GeO₂ were determined using standard quenching techniques. In contrast to published literature five congruently melting compounds were found to exist. They are Li₂O·7GeO₂, 3Li₂O O·8GeO₂, Li₂O O·GeO₂, 3Li₂O O·2GeO₂, and 2Li₂O.-GeO₂. The melting points, respectively, are 1033°± 5°C, 953°± 5°C, 1245°± 15°C, 1125°± 15°C, and 1280°± 15°C. Simple binary eutectic relations exist among the compounds. The eutectic temperature between 1:7 and GeO₂ is 1025°± 1h0°C at about 96.8 wt% GeO₂; the eutectic temperature between the 1:7 and 3:8 compounds is 935°± 10°C at about 90.9 wt% GeO₂; the eutectic temperature between the 3:8 and 1:1 compounds is 930°± 10 °C at about 89.8 wt% GeO₂. Liquidus data for compositions richer in lithia than the 1:1 compound are only approximate because of the difficulty of quenching them; the phase relations between the 1:1 and 3:2 and between the 3:2 and 2:l compounds, however, are found to be of the simple binary eutectic type. The glass–forming region was also determined. Melts allowed to cool in air crystallized. When, however, the melts were quenched, glasses containing as much as 8 wt% GeO₂ could be prepared in 5–g quantities. Both the refractive index–composition and density–composition curves for the glasses showed maxi–mums at about 6 to 8 wt% Li₂O.