Phase Separation Inducing Controlled Crystallization of GeSe₂–Ga₂Se₃–CsI Glasses for Fabricating Infrared Transmitting Glass–Ceramics

Abstract

Infrared transmitting glass-ceramics based on the selected glass of 65GeSe 2 -25Ga 2 Se 3 -10CsI were obtained by a two-stage heat-treatment method. Results of X-ray diffraction and scanning electronic microscopy indicated that droplet-like nanoparticles containing cubic Ga 2Àd Ge d Se 3 crystals are homogeneously generated in the glass-ceramics and that the whole glassceramic process is composed of phase separation, nucleation, and crystal growth. Evolutions of the optical and mechanical properties of glass-ceramics versus annealing time at the firststage heat treatment were also investigated. Compared with the parent glass, the fabricated glass-ceramics show considerably enhanced fracture toughness, practicable infrared transparence, and microhardness, which confer them with considerable competitive advantages over currently used infrared materials.

Transparent chalcogenide glass-ceramics

“…Recently, Liu and Lin have considered the chemical structure of GeGa-Se glassy matrices to understand the limit of glass composition leading to controllable glass-ceramics (Liu et al, 2009;Lin et al, 2011a). These papers give the key to understand the progressive crystallization of the glass network.…”

“…Thus, the choice of glass compositions mixing alkali halide within a covalent glassy matrix size has demonstrated its efficiency to make controllable crystals with various systems: Ge-Sb-Se-(CsCl/RbI/CsI), allowing a larger transmittance in the mid-IR up to 16 mm (Calvez et al, 2006;Liu et al, 2009). Some of the glass compositions have only demonstrated crystallization of the alkali halide compound when this last one is added in a high amount close to supersaturation.…”

“…VI (Chapter 10) Crystallization process in Ge-Ga-Se based chalcogenide glass-ceramics(Liu et al, 2009).Plate VII (Chapter 10) (a) Influence of MIE diffusion due to nanoparticles on the transmission in the short wavelength. (b) Influence of Rayleigh scattering due to microcrystals on the transmission in the mid-infrared range.…”

Nanoscale Inhomogeneities Mapping in Ga-Modified Arsenic Selenide Glasses

“…From purely implementation point, it is important to achieve a high enough concentration of RE ions in ChG. One of best solutions relies on introducing Ga (or In) into ChG matrix, permitting dissolution of higher ratio of RE dopants [8–13]. However, the Ga additions may essentially restrict glass-forming ability in many ChG systems [8, 11, 13–15] provoking parasitic devitrification processes at a nanoscale through phase separation, crystallite nucleation, growth, and extraction (uncontrolled spontaneous crystallization). Thus, it was shown, that in case of glassy As 2 Se 3 it is not possible to introduce more than 3 at.% of Ga without such intrinsic structural decomposition, which essentially influences the ChG functionality [8, 12, 14].…”

Molded Glass–Ceramics for Infrared Applications

“…Glass formation in systems such as GeSe 2 –Ga 2 Se 3 –CsI 11 or GeS 2 –Ga 2 S 3 –CsCl 12 has been explored and large vitreous domains have appeared. Several compositions have shown the ability to generate reproducible glass–ceramics and an increase of mechanical properties such as toughness compared with the base‐glass 13,14 . Even if the introduction of alkali‐halide leads to a larger transparency window and larger vitreous domain, it also lowers the chemical durability due to the hygroscopicity of halide salts 15 .…”