Additive Manufacturing of Zirconia‑Stabilized Silica-Phosphate Glasses from Sol-Gel-based Photocurable Inks

Transparent, rare-earth-doped silica-based glasses are promising candidates for photonic and laser applications due to their favorable optical properties. Here, we report the fabrication of three-dimensional silica-phosphate and silica-zirconia-phosphate (Nd³⁺-doped) glasses, using a sol-gel-derived, particle-free photocurable resin that is tailored for digital light processing (DLP) 3D printing and UV-assisted mold casting. The resin consists solely of sol-gel precursors and a dual photopolymerizable component, enabling high-resolution printing without particle dispersion. Following room-temperature aging and a short thermal treatment at 700 °C for 1 h, transparent, crack-free glasses were obtained. The resulting glass structures exhibited transmittance values of 76.2 ± 0.3 % and 77.1 ± 0.2 % at 680 nm and 850 nm, respectively, and retained an amorphous microstructure. Phosphate incorporation improved the distribution of Nd³⁺ ions and suppressed photoluminescence (PL) quenching, but partial phosphate loss occurred during sintering. The addition of zirconia effectively stabilizes the phosphate within the silica network, preserving the composition of the printing solution. Phosphate addition led to a pronounced enhancement of PL intensity, up to tenfold for the 92SiO₂-4P₂O₅-4ZrO₂ composition doped with 0.7 mol % Nd₂O₃, compared to phosphate-free glass (96SiO₂-4ZrO₂). This facile and combined photopolymerization and the sol-gel-based DLP printing process enable the fabrication of geometrically complex, compositionally tunable, transparent laser glasses, demonstrating a cost-effective route for developing custom photonic and optoelectronic components.