Effect of Ce/La Substitution on Optical Transparency and Ionic Conductivity of Sodium Silicate Glasses

We investigate sodium silicate glasses modified with Ce 2 O 3 and La 2 O 3 to explore the interplay between optical absorption, structure, and macroscopic properties. Ce doping drives a pronounced red‐shift of the absorption edge into the visible region (> 500 nm), arising from O 2− Ce 4+ charge‐transfer and intervalence transitions, accompanied by network depolymerization, minor reduction in ionic conductivity, and enhanced mechanical strength. La‐doped glasses, in contrast, maintain the UV absorption edge but strengthen the network with only weak depolymerization and limited conductivity reduction. Strikingly, in the La/Ce substitution series, the red‐shifted absorption is preserved while mechanical reinforcement and ionic conductivity are largely retained. This compositional window demonstrates that broadband optical absorption can be tailored without significant trade‐offs in structural or transport performance. The findings highlight the potential of Ce/La‐modified silicate glasses as stable, multifunctional UV‐visible‐blocking materials, with relevance for solar‐control windows, protective coatings, and photothermal applications.