Home Useful FTIR Info & Links IR Window Materials
Useful FTIR Info & Links
Window Selection Guide
Material Range (cm-1) Refractive Index
(at 2 µm) 		Mid-IR
%T Graph 		Properties
AgBr 22,000-286 2.30 A soft crystal; insoluble in water; darkens upon exposure to UV radiation; will cold flow.
AgCl 10,000-360 2.07 Soft crystal that is insoluble in water; darkens upon exposure to UV radiation; will cold flow.
Al2O3 (Sapphire) 50,000-1,650 1.7 Glass-like. Sapphire (Al2O3) is an extremely hard material which is useful for UV, NIR and IR applications through 5 microns.
AMTIR
(GeAsSe Glass)		 11,000-625 2.5 AMTIR (Amorphous Material Transmitting IR) is a glass; insoluble in water, resistant to corrosion.
BaF2 67,000-740 1.46 A hard, brittle crystal; insoluble in water; good resistance to fluorine and fluorides; no fog.
CaF2 77,000-1,110 1.42 A strong crystal; resists most acids and alkalis; withstands high pressure; insoluble in water; no fog.
CdTe 20,000-400 2.67   Lower thermal conductity than ZnSe (used with CO2 lasers). Attacked by oxidizers. Also known as Irtran-6.
Chalcogenide
(AsSeTe glass) 		4,000-900 2.8   Good for Mid-IR fiber optics; chemically inert.
CsI 40,000-200 1.74 Soft crystal; soluble in water; hydroscopic; offers an extended transmission range. Because this material is so soft and extremely hygroscopic, it is very difficult to polish.
Diamond 25,000-33 2.37   Phonon bands around 1900-2600, except in Type IIa diamonds. Very useful for high-pressure or corrosive work.
GaAs 7,000-650 3.33   Hard crystal, can be made amorphous
Ge 5,500-600 4.00 A hard, brittle crystal; insoluble in water; well suited for ATR.
Irtran-1 (see MgF2)
Irtran-2 (see ZnS)
Irtran-3 (see CaF2)
Irtran-4 (see ZnSe)
Irtran-5 (see MgO)
Irtran-6 (see CdTe) 		(Irtran is a registered trademark of the Eastman Kodak Company)
KBr 40,000-400 1.53 Very soft, water soluble crystal; low cost and good transmission range; fogs.
KRS-5
(Thallium Bromide-Iodide) 		20,000-250 2.37 A soft crystal, deforms under pressure; good ATR material. Soluble in bases and insoluble in acids. Toxic.
LiF 95,000-1,700 1.4   Best VUV transmitter available
MgF2 87,000-1,250 1.35  
NaCl 40,000-625 1.52 Very soft, water soluble crystal; low cost and good transmission range; fogs.
Polyethylene
(high density) 		600-30 1.54   Excellent for Far-IR, very cheap, attacked by few solvents, difficult to clean
Pyrex 30,000-4,000 1.473 Labware glass
Si 83,300-660 300-0 (depends on doping) 3.40 A hard and brittle crystal; inert; ideal material for far-IR.
SiO2 (Quartz) 65,000-2,700 1.4 A hard crystal, clear in the visible
ZnS
(Cleartran)		 17,000-833 2.2 A water-free form of ZnS. Insoluble in water. Also known as Irtran-2
ZnSe 17,000-720 2.2 A hard and brittle crystal; inert; ideal material for ATR. Also known as Irtran-1.
Display # 
# Web Link Hits
1   Link   International Crystal Laboratories
Spectroscopy Optics and Supplies 		682
2   Link   Sigma-Aldrich IR Crystal Windows
Product Catalog → Labware → Spectroscopy Supplies → Spectroscopy, IR → Crystal Windows 		792
3   Link   FTIR.com Optical Elements
optical elements used in IR spectroscopy 		788
4   Link   ISP Optics Material Characteristics
370
 

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