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 Sc3+-based nanocrystals from glass is rarely reported and the incorporation of lanthanide activators into the Sc3+-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 KSc2F7 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 KSc2F7 and the partition of Ln dopants into the KSc2F7 lattice by substituting Sc3+ ions. Importantly, modifying the Ln-to-Sc ratio in glass enables to control competitive crystallization of KSc2F7 and Ln-based (KYb2F7, KLu2F7, and KYF4) 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 Ln3+ 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.