Bismuth-rich phosphate glasses: Synthesis, characterization, and Bi0 nanoparticle formation

Bismuth phosphate glasses possess remarkable properties such as a high refractive index (∼1.9), low characteristic temperatures, thermal stability against crystallization, and an appreciable transparency window spanning from ultraviolet (UV) to near infrared (NIR). These characteristics make them promising materials for optical devices and photonic applications. This study focuses on investigating the properties of a novel bismuth-rich phosphate glass system with a ternary composition of Bi(PO 3 ) 3 −Bi 2 O 3 −Na 2 O. The synthesis was carried out using the conventional melt-quenching method in alumina crucibles under ambient air conditions. Structural and optical properties of the newly developed glass system were assessed using Raman and UV-Vis spectroscopies, differential scanning calorimetry (DSC), and 31 P. and 23 Na nuclear magnetic single and double resonance. The 31 P-NMR and Raman analysis reveal the depolymerization of the metaphosphate network with Bi 2 O 3 and Na 2 O, acting as classical network modifiers with the theoretically expected conversion rates of three and one bridging oxygen per equivalent, respectively. The tendency of nanoparticle formation increases with the concentration of Bi 2 O 3 . UV-vis spectroscopy demonstrates that the values of the optical band gap are correlated with the modifier concentration. In addition, they indicate the formation of Bi 0 nanoparticles. Transmission electron microscopy (TEM) images identified nanoparticles of spherical shape, ranging from 4 to 70 nm in diameter. In summary, the results demonstrate a promising novel phosphate glass system containing high concentrations of bismuth atoms, with the potential for elemental Bi 0 nanoparticle formation.