Yttrium-dopants-induced phase-controllable and luminescence-tunable lanthanide-doped α/β-NaYbF4 nanocrystals in glass for laser-driven upconverted lighting

In-situ glass crystallization is an effective way to integrate lanthanide-doped upconversion nanocrystals into amorphous glass, producing bulky nanocomposites for specific applications. However, the precipitation of hexagonal NaYbF4 nanocrystals from glass is rarely reported owing to the preferred crystallization of cubic phase. Herein, phase-controllable in-situ crystallization of cubic/hexagonal NaYbF4 nanocrystals in glass is achieved via Y3+ doping. A series of structural and spectroscopic characterizations evidence the formation of Na (Yb/Y)F-4 solid-solution nanocrystals in glass and the incorporation of lanthanide emitting centers (Er3+, Tm3+, Eu3+) into the crystalline lattice. Introducing high-content Y3+ dopants is beneficial to induce the crystallization of hexagonal NaYbF4 phase in glass and enables elaborated tunability of Er3+ upconversion emissive colors. Finally, a prototype upconverted solid-state-lighting device is constructed by coupling 980 nm laser with the as prepared Er/Tm doped monolithic glasses containing Na(Yb/Y)F-4 nanocrystals, producing bright upconversion white-light with luminous efficiency of 1 lm/W and energy efficiency of 0.5%.