Infrared-transparent glass ceramics: An exploratory study

Abstract

a b s t r a c tIn this work, the vision and need for a fully ceramized long-wave infrared (LWIR)-transmitting glass ceramic have been articulated. Three sulfide systems were explored including two with La 2 S 3 in hopes of imparting strong bonds from this refractory sulfide, and two containing GeS 2 in hopes of widening the glass-forming region. Attempts were made to produce glasses in the Ga 2 S 3 -La 2 S 3 -(ZnS,CaS) system, the GeS 2 -La 2 S 3 system, and the GeS 2 -Ga 2 S 3 -CdS system. Water quenching produced glasses of Ga 2 S 3 -La 2 S 3 -CaS and GeS 2 -Ga 2 S 3 -CdS. Microstructural and thermal analyses were used to explore nucleation and growth in these systems and infrared transmission and mechanical hardness showed potential for LWIR window use. The GeS 2 -Ga 2 S 3 -CdS system showed good LWIR transmission and pre-crystallized hardness superior to chemical vapor deposited ZnS. The Ga 2 S 3 -La 2 S 3 glasses did not appear to be viable candidates at this time due to a small temperature window between crystallization and glass transition temperatures and problems with oxygen contamination in the La 2 S 3 source. Suggestions are made for two alternative methods for producing fully ceramized LWIR-transmitting glass ceramics.

Influence of phase separation on structure–property relationships in the (GeSe2–3As2Se3)1−xPbSex glass system

“…Numerous references describe how this has been employed in commercial applications. (11)(12)(13)(14)(15) Phase separation effects are of general interest in glass science, as it can give rise to pronounced changes in physical, thermal and optical properties of network glasses which may be useful or detrimen-tal. (16,17) Detailed characteristics of phase separated glasses depend strongly on the nature and volume fraction of the phases developed.…”

“…(19) Related efforts examining infrared (IR) glass-ceramics have been reported which may or may not (deliberately) exploit phase separation as a stepping stone to controlled crystallization. (13,14,20) Oxide and non-oxide glasses possess compositions known to exhibit phase separation, though literature on specific aspects in non-oxide systems (such as phase diagrams and immiscibility boundaries) is limited with a few noteworthy exceptions. (21) As discussed below, such glass compositions possess large, positive enthalpies of mixing in the liquid state resulting in instability that can vary with composition.…”

Nano-Structured Optical Fibers Made of Glass-Ceramics, and Phase Separated and Metallic Particle-Containing Glasses

“…Efforts have been also focused on the preparation of GCs transparent up to 12 µm using chalcogenide glasses. The crystallization of chalcogenide glasses has been of great interest [168][169][170][171][172][173][174]. However, the crystallization of these glasses is difficult to control, as reported in [173]; Zhang et al reported that, as for oxide glasses, the control of the nucleation and crystal growth is very sensitive to temperature and to the glass composition.…”

Impact of Morphology and Microstructure on the Mechanical Properties of Ge-As-Pb-Se Glass Ceramics

“…The main limitation in realizing a greater number of candidate glass families suitable for controlled crystallization is poor glass-forming ability and the change in optical properties when a nucleating agent is introduced [4]. The addition of nucleating agents has been shown to result in undesirable effects such as phase separation, spontaneous crystallization of the entire glass upon cooling, as well as reduced crystal growth control [23]. Some groups have investigated the formation of GCs in ChGs to increase mechanical hardness and toughness [17,[24][25][26][27][28][29][30][31][32], but a systematic correlation between starting glass morphology (homogeneous glass versus phase separated glass) and glass-crystal volume fractions in a GC, and the respective corresponding impact on the mechanical properties of ChG ceramics, has not to our knowledge been carried out.…”

“…In this study, we have focused on the measurement of the glass and GC's micro-indentation response as quantified by Vickers hardness, and a variation in the materials Young's modulus following heat-treatment. A multicomponent ChG is the subject of the study, GeSe 2 -As 2 Se 3 -PbSe (GAP-Se), which possesses good transparency in the IR region and exhibits the requisite narrow size distribution of the secondary crystallized phase(s) making it suitable as an optical nanocomposite [23,35,41]. Such behavior enables the use of a controlled crystallization protocol to realize high RI nanocrystals for GRIN applications.…”