Structural, physical and thermal properties of lead germanate glasses

·Study of lead germanate glasses by neutron diffraction, RMC, DSC and Raman analysis.·Density increases while Tg and atomic number density decrease with an increase in PbO mol%.·Ge-O co-ordination essentially tetrahedral and in the range: 3.9 to 4.2(1).·Small amount of GeO3 and GeO5 but no GeO6 units in glass structure.·Pb-O co-ordination decreases from 4.0 to 3.1(1) with increase in PbO mol%. The effects of PbO concentration on the density, thermal and structural properties of xPbO–(100-x)GeO2 (x = 20 to 55 mol%) glasses were studied. Density of glasses increases linearly from 5.043 to 6.981(5) g·cm−3, while the glass transition temperature decreases drastically from 467 °C to 359 °C on increasing PbO concentration from 20 to 55 mol%. Neutron diffraction studies found that Ge-O co-ordination is in the range: 3.9–4.2(1), and there is a very weak germanate co-ordination anomaly at PbO concentration of 40 and 50 mol%. GeO4 are the dominant structural units with a small quantity of GeO3 and GeO5 but very little GeO6 in the glass network. Pb-O and OO co-ordination decreases with an increase in PbO mol% and are in the range of: 4.0–3.1(1) and 6.3–5.4(1) respectively. Raman studies indicate a decrease in Pb-O co-ordination with increase in PbO mol%, in good agreement with the neutron diffraction findings.