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

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.