Low thermal expansion ZBLAN‐based glass ceramics containing CaZrF₆ crystals

Abstract

Fluoride glass is considered as an excellent optical material owing to its ultralow phonon energy (578 cm −1 ). However, its high thermal expansion coefficient (15.87 × 10 −6 /K) and deformability severely limit applications under service environments with high temperature, high humidity, and high-power irradiation. To overcome these limitations, we developed a ZBLAN-based fluoride glass ceramics (CZBLAN GCs) contained the negative thermal expansion material-CaZrF 6 crystals by phase-separation engineering. The ability to control the precipitation of the desired crystal phase was achieved by adequate compositional design for phase separation, yielding improved or new properties in the development of fluoride GCs. With the successful precipitation of very uniformly dispersed single CaZrF 6 crystals in the glass phase (up to ∼40% crystallinity), a significantly lower thermal expansion coefficient (3.66 × 10 −6 /K) in the fluoride system was achieved. Moreover, enhanced fluorescence properties of Eu-doped CZBLAN GCs were observed compared with those of Eu-doped ZBLAN glass owing to the lower phonon energy in GCs.

Transparent fluoride glass-ceramics with phase-selective crystallization for middle IR photonics

“…9,21 Recently, we developed a new facile one-step route with concurrent rapid-quenching-crystallization for the phase-selective crystallization in fluoride glass, which was achieved via the unique combination of liquid phase-separation engineering and rapid quenching. [22][23][24] Phase-separation, a pre-nucleating process without crystal formation, is used to trigger spontaneous crystallization in a fluoride glass melt during the cooling stage. 25,26 This is achieved via the introduction of specific cations with selection of field strength that can induce the desired phase separation.…”