Oxyfluoride Glass-Ceramics for Transition Metal Ion Based Photonics: Broadband Near-IR Luminescence of Nickel Ion Dopant and Nanocrystallization Mechanism

Nickel ion doped transparent bulk glass-ceramics containing K2SiF6, ZnF2, and KZnF3 nanocrystals were elaborated to show the prospect that this novel group of oxyfluoride glass-ceramics is promising for transition metal ion based photonics. These new oxyfluoride glass-ceramics exhibit a new broadband luminescence of Ni2+ ions in the intriguing near-IR spectral region ranging from 1200 to 2400 nm. Ni2+ ions are incorporated into the precipitated K2SiF6, ZnF2, and KZnF3 crystals, which provide octahedral sites for Ni2+ and make it optically active. Taking into account the microstructure of phase separation observed by replica TEM, a detailed mechanism of phase-separation-assisted nanocrystallization was described for these oxyfluoride glasses. These results allow one to establish a full physical model of the nanocrystallization mechanism. For the precipitation of fluoride crystallites, not only can the nanometric size be explained but also the formation of different crystal phases can be controlled by the initial amorphous phase separation of droplet or interpenetrating structure with a sufficiently elaborated glass design.