Structural and magnetic properties of Gd3+ ions in sodium–lead borophosphate glasses

Glasses in the (30 − x) (NaPO3)6 + 30PbO + 40B2O3 + x Gd2O3 system with x = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mol% have been prepared by the melt quenching method. The electron paramagnetic resonance (EPR) and FT-IR spectra of these glasses have been studied. The EPR spectra of sodium–lead borophosphate glasses at room temperature exhibit three prominent features with effective g-values of ≈5.99, 2.85 and 1.98 and weaker features at g ≈ 3.60 and 4.77. The EPR spectra of these glasses containing 1.0 mol% Gd3+ ions have been studied at different temperatures (93–303 K). The spin concentration (N) participating in resonance for g ≈ 5.99 resonance signal has been calculated as a function of Gd content and temperature. It is observed that N increases with Gd content. A linear relationship is established between log N and 1/T and the activation energy is calculated from the graph. The paramagnetic susceptibility (χ) is calculated from the EPR data at various temperatures and the Curie constant (C) and paramagnetic Curie temperature (θp) have been evaluated from the 1/χ versus T graph. The emission and excitation spectra are measured and it is found that the Gd3+ ions doped glasses exhibit good UV-excited luminescence. The IR spectra of the borophosphate glasses reveal prominent IR absorption spectrum which is characterized by well-defined bands in the far- and mid-IR region. The IR results depict the presence of BO3, BO4, and PO4 structural units. The theoretical values of optical basicity (Λth) of the glasses have also been evaluated.