UV upconversion luminescence of highly Pr3+-doped silica-based glasses prepared by gas levitation melting

Pr3+-doped aluminosilicate glasses were prepared by gas levitation melting, enabling high rare-earth incorporation beyond the conventional solubility limit of silica-based systems. Under 455 nm excitation, a broad ultraviolet emission band peaking at ∼291 nm was observed and assigned to the 4f15d1 → 4f2 transition of Pr3+, demonstrating UV upconversion in a silica-based glass matrix. The upconversion intensity showed a strong dependence on Pr3+ concentration, with a maximum at ∼0.1 mol %, while higher concentrations led to significant quenching. Raman spectra revealed that increasing Pr3+ content induces local structural ordering, indicating limited solubility and its impact on luminescence performance. The addition of Al2O3 significantly enhanced both upconversion and photoluminescence intensities, with an optimum at intermediate Al content. This enhancement is rationalized by improved spatial distribution of Pr3+ ions and suppression of concentration quenching, while excessive Al results in reduced emission due to structural over-modification. These results demonstrate that UV upconversion in silica-based glasses is governed by the interplay between local structure, dopant concentration, and host-dependent electronic states. Gas levitation melting combined with compositional control provides an effective route to expand the accessible composition range and optimize luminescence properties.