Phase Relations and Glass Formation in the System PbO‐GeO,

Phase relations in the system PbO‐GeO 2 were determined using the quenching technique. The five compounds detected were: 4PbO‐GeO 2 , 3PbO‐2GeO 2 , PbO‐GeO 2 , and PbO‐4GeO 2 . The 3:2 and 1:1 compounds melt congruently at 744° and 799°, respectively. The 4:1 compound melts incongruently at 726°C to PbO plus liquid, whereas the 1:4 compound melts incongruently to GeO 2 plus liquid at 790°C. The 1:2 compound has a temperature range of stability between 707° and 730°. The data indicate that no liquid immiscibility gap exists in the system. Indices of refraction for glasses in the system were compared with lead silicate glasses. An addition of ∼65%PbO to GeO 2 is required to prepare a glass with an index near 2.0 whereas with SiO 2 , ∼85% PbO is required. It appears that the lead germanate glasses have higher indices than all other two‐component oxide glasses. The addition of PbO to GeO 2 decreases the rutile‐to‐quartz transformation temperature from 1000°C for pure GeO 2 to 990°C. Infrared spectra of lead germanate glasses (∼60w% PbO) show that transmission is good up to 5.5μ but decreases drastically between 5.5 and 6.5μ.