Phase Equilibria in the System Li2O-BeO-SiO2

The equilibrium phase diagram for the system Li₂O-BeO-SiO₂ contains only one ternary compound, Li₂BeSi0₄. Liquidus relations for compositions containing 33 mol% SiO₂ were determined; 10 liquidus invariant points were located and 7 subsolidus compatibility triangles. The most refractory compositions lie on the join BeO-Li₂BeSiO₄, with a solidus temperature of 1320°C. Metastable phases observed were a high-quartz phase, Li_2x(Si₁-_xBe_x)O₂, x 0.33; phase X which is probably a metastable orthosilicate between Li₂BeSiO₄ and Be₂SiO₄; and phase Y which lies on the join Li₂BeSiO₄-SiO₂. The crystal chemistry and glass network-forming properties of BeO are discussed.