Abstract
Phase relations in the system PbO‐GeO2 were determined using the quenching technique. The five compounds detected were: 4PbO‐GeO2, 3PbO‐2GeO2, PbO‐GeO2, and PbO‐4GeO2. 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 GeO2 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 GeO2 is required to prepare a glass with an index near 2.0 whereas with SiO2, ∼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 GeO2 decreases the rutile‐to‐quartz transformation temperature from 1000°C for pure GeO2 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.
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