Simultaneous Tailoring of Dual-Phase Fluoride Precipitation and Dopant Distribution in Glass to Control Upconverting Luminescence.

In situ glass crystallization is an effective strategy to integrate lanthanide-doped upconversion nanocrystals into amorphous glass, leading to new hybrid materials and offering an unexploited way to study light-particle interactions. However, the precipitation of Sc-based nanocrystals from glass is rarely reported and the incorporation of lanthanide activators into the Sc-based crystalline lattice is formidably difficult owing to their large radius mismatch. Herein, it is demonstrated that lanthanide dopants with smaller ionic radii can act as nucleating agents to promote the nucleation/growth of KScF nanocrystals in oxyfluoride aluminosilicate glass. A series of structural and spectroscopic characterizations indicate that Ln-dopant-induced K/Sc/Ln/F amorphous phase separation from glass is an essential prerequisite for the precipitation of KScF and the partition of Ln dopants into the KScF lattice by substituting Sc ions. Importantly, modifying the Ln-to-Sc ratio in glass enables to control competitive crystallization of KScF and Ln-based (KYbF, KLuF, and KYF) nanocrystals and produce dual-phase fluoride-embedded nanocomposites with distinct crystal fields. Consequently, tunable multicolor upconversion luminescence can be achieved through diversified regulatory approaches, such as adjustment of the dual-phase ratio, selective separation of Ln dopants, and alteration of incident pumping laser. As a proof-of-concept experiment, the application of dual-phase glass as a color converter in 980 nm laser-driven upconverting lighting is demonstrated.