Fe-dependent optical properties of peralkaline soda aluminosilicate glasses: a combined Raman and photoluminescence study

This study investigates the influence of iron on the optical properties of peralkaline soda aluminosilicate glasses (NASF), focusing on the interplay between glass structure and optical behavior. Fe doping significantly affects the glass network, altering both its structural connectivity and optical properties. Raman spectroscopy reveals that Fe modifies the glass structure by increasing non-bridging oxygens (NBOs), reducing network connectivity. For the highest FeO tot concentration of 8.2 at.%, a more polymerized structural reorganization occurs due to iron self-compensation. Optical analysis shows that Fe incorporation increases the optical absorption and shifts the absorption edge to higher wavelengths. Tauc plot calculations reveal a decrease in the optical bandgap from 4.0 to 3.2 eV, while the Urbach energy indicates an increase of structural disorder. The photoluminescence (PL) excitation and emission related to Fe 3+ energy levels is observed, with a broad red emission peak at 700 nm, decreasing with Fe concentration in relation to higher defectivity and clustering. A detailed lifetime analysis shows long lasting tails of the order of milliseconds, also decreasing with Fe content due to non-radiative recombinations and quenching. • A detailed structural and optical investigation of iron doped soda aluminosilicate glasses was obtained by Raman and photoluminescence spectroscopy; • Increasing FeO tot concentration, the network becomes more and more depolymerized, but above 8.2 wt% iron coordination shifts from six- to four-fold, re-polymerizing the network. • The optical energy gap was obtained by Tauc plot analysis, revealing a decrease as a function of the iron content. • The defectivity of the material increases with iron content as shown by Urbach energy trend. • Photoluminescence characterization showed the specific energy transition of Fe 3+ ions, decreasing in intensity and lifetime with the increase of iron content, in agreement with previous structural and defectivity analysis.