Luminescence and structural evolution in ultra-low melting quaternary tin fluorophosphate glasses (NaF-SnF2-SnO-P2O5)

For transparent low melting inorganic glass, which is relevant for sealing and additional applications, Pb-containing glasses have reached the lowest melting point and best comprehensive performance. Considering potential toxicity and regulatory limitations, there is urgent need to develop Pb-free ultra-low melting point glass. Herein, we systemically investigated the structure and luminescence evolution of the Pb-free ultra-low melting quaternary tin fluorophosphate glasses (NaF-SnF2-SnO-P2O5), in which varied NaF content was tuned to affect the properties of glass. With NaF content increases, the Sn-O and P-O bonds have been gradually transformed to Sn-F and P-F bonds, and the phosphrous tetrahedron PO4 has been converted to PO3F. The weaken bonding results in the decrease of the ultra-low melting point to 329 degrees C when NaF increased to 15 a.t.%, 29(o)C lower than the ternary glass. The blue shifts of both absorption and photoluminescence spectra were observed due to the higher ionic character of glass structure with NaF increases. As reported previously in the ternary tin fluorophosphate glass, the quaternary glass system also shows a phosphorescence behavior (similar to 1 s) due to the existence of oxygen vacancies. Additionally, the changes in oxygen vacancy defects correlate with the NaF content, thus affecting the decay time as well. The ultra-low melting point luminescent quaternary tin fluorophosphate glasses (NaF-SnF2-SnO-P2O5) may be relevant for opto-electronic applications such as the packaging in displays or light-emitting diodes.

Automated summary

By systematically investigating the structure and luminescence evolution of Pb-free ultra-low melting quaternary tin fluorophosphate glasses with varied NaF content, this study successfully reduces the melting point and enhances the ionic character of the glass structure. Additionally, the presence of oxygen vacancies in the quaternary glass system affects the decay time and leads to potential applications in opto-electronics.