Phase-Selective Nanocrystallization of NaLnF4 in Aluminosilicate Glass for Random Laser and 940 nm LED-Excitable Upconverted Luminescence

Yb/Er doped hexagonal beta-NaLnF(4) (Ln = Gd, Y, Lu) are regarded as the most efficient green upconversion (UC) materials. Unfortunately, beta-NaLnF(4) is quite difficult to grow as monocrystal owing to cubic-to-hexagonal phase transition during cooling. As an alternative, herein a nanocrystallization controllable strategy to synthesize monodisperse whole-family beta-NaLnF(4) (from NaLaF4 to NaLuF4) embedded bulky glass ceramics is reported. A series of structural and spectroscopic characterizations indicate that Na content and Al/Si ratio are the most important factors to determine phase-selective NaLnF(4) crystallization in the aluminosilicate oxyfluoride glasses. Impressively, such nanocomposites are evidenced to be ideal hosts for upconversion luminescence of Yb3+/Er3+ dopants and as the proof-of-concept experiments, their applications in a random laser and incoherent LED-excitable upconverting device as emitting media are demonstrated. It is expected that this study will provide a deep understanding for controllable crystallization in glass and extend the practical applications of glass ceramics in optoelectronic fields.