Exploring the Influence of ZnF₂ on Zinc-Tellurite Glass: Unveiling Changes in OH Content, Structure, and Optical...

Tellurite glasses have garnered considerable interest as optical host materials due to their advantageous properties, including low processing temperature, high resistance to corrosion and crystallization, and excellent solubility for rare earth ions. However, their applicability in the infrared (IR) region is limited by the absorption of species with distinct vibrations. The incorporation of fluorides has emerged as a promising approach to reduce hydroxyl (OH) absorption during the precursor melting process. In this study, we investigated the influence of ZnF₂ on a glass matrix composed of TeO₂-ZnO-Na₂O, resulting in notable changes in the glass structure and optical properties, with Eu³⁺ serving as an environmental optical probe. The samples underwent comprehensive structural, thermal, and optical characterization. Structural analyses encompassed ¹⁹F and ¹²⁵Te nuclear magnetic resonance (NMR), with the latter being complemented by mathematical simulations, and these findings were consistent with observations from Raman scattering. The main findings indicate an enhancement in thermal stability, modifications in the Te-O connectivity, and a reduction in emission intensity attributed to the effects of ligand polarizability and symmetry changes around Eu³⁺. Additionally, the fluorotellurite matrices exhibited a shift in the absorption edge toward higher energies, accompanied by a decrease in mid-IR absorptions, thereby expanding the transparency window. As a result, these glass matrices hold substantial potential for applications across various regions of the electromagnetic spectrum, including optical fiber drawing and the development of solid-state emitting materials.