Structural investigations of lead germanosilicate glasses doped with Nb2O5 by means of spectroscopic and dielectric studies

• Nb2O5 doped lead germanosilicate glasses are synthesized by melt quenching technique.
• The absorption bands observed around 325 and 340 nm are due to Ge2+ state.
• FTIR and Raman studies indicated that NbO6 units have depolymerized the glass matrix.
• Glasses doped with 2 mol% of Nb2O5 exhibit the better conducting nature.

The transparent glasses with composition 30PbO–10GeO2–(60−x)SiO2−xNb2O5 (mol%) (0 ≤ x ≤ 2.5) are prepared by conventional melt quenching technique. The amorphous nature of the prepared glasses is characterized by XRD. The spectroscopic studies such as optical absorption, FTIR, Raman spectra were carried out at room temperature on these glasses. Besides this electrical properties, like dielectric constant ε'ε', loss tanδδ, ac conductivity σacσac etc., were also investigated over a moderately wide range of frequency (103–106 Hz) and temperature (30–300 °C). The optical absorption spectrum of the prepared glasses has exhibited absorption bands around 325 nm and 340 nm and these are due to the triplet – singlet electronic transition of Ge2+ state presents in the glass matrix as conversion of GeO2 into GeO is much easier rather than SiO2. From FTIR spectra of as prepared glasses, it is noticed that the intensity of octahedral NbO6 structural units is found to increase up to 2 mol% of Nb2O5 there after it is observed to decrease. It is also supported by Raman shift of NbO6 structural units observed around 650 and 930 cm−1. The analysis of electrical studies is also revealed that the conductivity of prepared glasses is found to increase gradually up to 2 mol% of Nb2O5 beyond this concentration it is observed to decrease. When the spectroscopic investigations are coupled with electrical studies it is concluded that the glass samples doped with 2 mol% of Nb2O5 are found to exhibit good semiconducting nature among the prepared glasses. Such glasses are suitable for fabrication of solid state devices.