Influence of Pr6O11 Concentration on the Thermal, Structural, Physical, and Optical Behavior of SNW Glass Systems.

Praseodymium-doped antimony-phosphate glasses with the composition 47.5Sb2O3-47.5NaPO3-5WO3-xPr6O11 (x = 0.05, 0.1, 0.25, 0.3 mol%) were synthesized by melt-quenching and characterized by DSC, FTIR, density, hardness, ultrasonic, and UV-Vis techniques. Tg (314.26°C-320.61°C) and ΔT (40.12°C-59.07°C) showed limited variation, with highest stability for the undoped glass. FTIR confirmed phosphate groups (P-O-P, PO3 2-, PO2 -) and increasing NBO, indicating Pr-induced depolymerization. Density decreased (4.2735-4.2223 g/cm3), while hardness increased (254-289 kg/mm2). Molar volume (48.47-49.76 cm3/mol), oxygen molar volume (16.16-16.40 cm3/mol), and molar refraction increased, reflecting a more open, polarizable structure. Elastic moduli increased up to 0.25-mol% Pr then slightly decreased. The optical band gap decreased (3.079-3.022 eV), Urbach energy increased (0.350-0.374 eV), and refractive index increased with Pr content. The results indicate that Pr6O11 functions as an effective network modifier, promoting controlled depolymerization and enhanced optical tunability while preserving thermal stability and mechanical integrity. Among the studied compositions, 0.25-mol% Pr6O11 provides the optimal balance between structural rigidity, optical properties, and mechanical strength, making these glasses promising candidates for composition-tunable active photonic media, particularly in broadband optical amplifiers, visible-near infrared solid-state laser hosts, and high-refractive-index waveguide components, where the combined enhancement of refractive index, mechanical strength, and electronic polarizability enables efficient light confinement and emission control.