Structural and optical properties of the gadolinium–lead–germanate glasses

Abstract

Glasses in the system xGd 2O 3(100 − x)[7GeO 2·3PbO] with 0 ≤ x ≤ 40 mol% have been prepared from melt quenching method. The influence of gadolinium ions on structural behavior in lead–germanate glasses has been investigated using FTIR, UV-VIS and EPR spectroscopy. The structural changes have been analyzed with increasing rare earth concentration. FTIR data suggest that the glass network modifications has taken place mainly in the germanate part whereas the lead part remained unmodified and its network consists mainly from the [GeO 4], [GeO 6], [Ge 2O 7] structural units and with interconnected through Ge–O–Ge bridges in [GeO 4] structural units. The changes in amplitude and bandwidth of the UV-VIS bands ranging from 200 nm to 350 nm depend on the content of Gd 2O 3. By increasing the Gd 2O 3 content in the glass matrix, the optical band gap energy increases, indicating changes of the lattice parameters and that no non-bridging-oxygens form upon the addition of gadolinium oxide. The decreasing trend has been observed both in optical gap band energy and refractive index of oxide glasses at x = 10 mol% Gd 2O 3 indicating breaks up the [GeO 4] tetrahedral units bonds and create of non-bridging oxygen atoms. For sample with x ≥ 20 mol%, the gadolinium ions having a behavior of network formers ( g ≈ 4.8) will coordinate more with the excess of oxygen. Accordingly, the gadolinium ions are generally suspected to improve their environment of network formers.