| Material | SWL (cm-1) | LWL (cm-1) | Refractive Index | S/D | Flatness | Pe Atm | Restrahlen (cm-1) | Density g/cc | Solubility (g/100g) | Melting Point (°C) | Hardness kg/mm2 | Comments |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AgBr | 22,000 | 255 292 |
2.22@10 | 80/50 | 5 | 0.56 | 88 | 6.5 | 1.2E-05 | 432 | 7 | Insoluble in water, slightly soluble in sodium hydroxide and some amines. Migrates into base metals. Will blacken under UV radiation. Cold flows and should not be used above 200 °C. |
| AgCl | 24,500 | 353 404 |
1.90@10 | 80/50 | 5 | 0.56 | 123 | 5.6 | 5.2E-02 | 457 | 10 | Insoluble in water, slightly soluble in sodium hydroxide and some amines. Migrates into base metals. Will blacken under UV radiation. Cold flows and should not be used above 200 °C. |
| Al2O3 | 40,000 | 1608 1834 |
1.76@0.6 1.77@0.6 |
40/20 | 1/2 | 6.1 | 741 | 4.0 | 0 | 2040 | 1370 | GRAS. Resistant to strong acids and bases. Birefringent. Very durable and may be used at high temperatures. |
| AMTIR | 11,000 | 593 625 |
2.50@10 | 80/50 | 1 | 0.27 | 4.4 | 0 | 370 | 170 | Amorphous material. A chalcogenide glass, which, although relatively hard, is also brittle. Insoluble in water and resistant to acids. It is attacked by alkalis. | |
| BaF2 | 66,600* | 691 782 |
1.45@5 | 40/20 | 1/20 | 0.56 | 213 | 4.9 | 0.17 | 1280 | 82 | Hard material suitable for high pressure applications. Extremely vulnerable to thermal shock. Very slightly soluble in water. Attacked by ammonium hydroxide, ammonium salts, complex agents such as EDTA, and acids. |
| CaF2 | 79,500* | 896 1025 |
1.40@5 | 40/20 | 1/20 | 0.77 | 286 | 3.2 | 0.0017 | 1360 | 158 | Very hard material similar to BaF 2 , but almost insoluble in water and less vulnerable to thermal shock. Attacked by nitric acid and strong hydroxides, ammonium salts, and complexing agents such as EDTA. Very desirable for near-IR applications as it has no OH absorption bands. |
| CdTe | 17,000 | 313 340 |
2.67@10 | 80/50 | 1 | 0.08 | 6.2 | 0 | 1092 | 56 | Hard but very brittle material. Insoluble in water. Attacked by nitric acid. | |
| Cleartran | 22,000 | 690 722 |
2.20@10 | 40/20 | 1/20 | 2.2 | 328 | 4.1 | 0 | 1830 | 240 | GRAS. A clear form of ZnS. Properties similar to ZnS. |
| CsI | 42,000 | 172 | 1.73@10 | 80/50 | 1/10 | 0.12 | 69 | 4.5 | 44 | 621 | 1 | Soft and hygroscopic. Generally only used for its extended far-IR transmission. Should only be exposed to anhydrous solvents. Never use with alcohols or aqueous solutions. A hard optical coating can be used to provide some protection. In powdered form it can be used to make pellets. Keep stored in a dessicator or heated cabinet. |
| Diamond | 30,000 | 2 | 2.41@0.6 | 20/10 | 1 | 10.9 | None | 3.5 | 0 | 550fp | 5700 | GRAS. Hard and chemically resistant. Often used in very high pressure applications. High cost limits size to a few mm. Has a characteristic lattice absorption doublet between 1800 and 2700 cm -1 . |
| Ge | 5500 | 432 574 |
4.00@10 | 60/40 | 1/8 | 1.0 | None | 5.3 | 0 | 936 | 780 | Hard and brittle. Semiconductor material with low band gap energy. Free electron absorption becomes important at temperatures above about 60 °C and it can become totally opaque at temperatures above 100 °C. Attacked by sulfuric acid and aqua regia. When used as a window it has high reflection losses which can be significantly reduced with BBAR coatings. Used as an ATR prism when low penetration depth is desired. |
| KBr | 48,800 | 345 388 |
1.52@10 | 60/40 | 1/20 | 0.02 | 129 | 2.8 | 53 | 730 | 6 | The most popular IR material. Hygroscopic and can only be used with anhydrous solvents, glycerol or alcohols. Withstands thermal and mechanical shock well. A protective coating can improve its resistance to humidity. Keep stored in a dessicator or heated cabinet. |
| KCl | 55,600 | 385 439 |
1.45@10 | 60/40 | 1/20 | 0.05 | 158 | 2.0 | 35 | 776 | 7 | Hygroscopic and can only be used with anhydrous solvents, glycerol or alcohols. Withstands thermal and mechanical shock fairly well. A protective coating can improve its resistance to humidity. When AR coated can be used as a low cost CO 2 laser window. Keep stored in a dessicator or heated cabinet. |
| KRS-5 | 17,900 | 204 232 |
2.37@10 | 60/40 | 1/1 | 0.56 | 74 | 7.4 | 0.05 | 414.5 | 40 | Extremely toxic, even with skin contact. KRS-5 should only be handled with protective gloves or finger cots. A relatively soft material, it cold flows and deforms under pressure. This is enhanced at temperatures above 200 °C. It should only be polished by well-trained professionals. Good chemical resistance. |
| LiF | 96,150* | 1105 1286 |
1.39@0.5 | 40/20 | 1/10 | 0.23 | 400 | 2.6 | 0.27 | 870 | 105 | Slightly soluble in water. Hard and brittle. Sensitive to thermal shock. Should not be used above 400 °C. |
| MgF2 | 90,900* | 1271 1457 |
1.38@0.51.39@0.5 | 40/20 | 1/20 | 1.0 | 500 | 3.2 | 0.0002 | 1255 | 415 | Almost insoluble in water. Can be used at fairly high pressure. Slightly sensitive to thermal shock. Birefringent. Should not be used above 500 °C. |
| NaCl | 52,600 | 457 584 |
1.49@10 | 40/20 | 1/20 | 0.05 | 200 | 2.2 | 36 | 801 | 18 | Harder and less hygroscopic than KBr but can only be used with anhydrous solvents, glycerol or alcohols. Withstands thermal and mechanical shock fairly well. A protective coating can improve its resistance to humidity. Keep stored in a dessicator or heated cabinet. |
| Si | 8900 | 624 969 |
3.41@10 | 60/40 | 1/8 | 1.8 | None | 2.3 | 0 | 1420 | 1150 | Hard material and resistant to most chemicals except for strong acids. Withstands thermal shock. Has a strong phonon absorption band at 590-630 cm -1 . Transmits well at wavenumbers lower than this and well into the far-IR. BBAR coatings are available for the mid-IR region. |
| SiO2 | 50,000* | 2315 2677 |
1.53@1 | 40/20 | 1/20 | 4.2 | 2.6 | 0 | 1713 | 460 | GRAS. Resistant to acids and alkalis. Used in the near-IR. Most forms of SiO 2 have OH absorption bands. | |
| ZnS | 17,000 | 690 722 |
2.20@10 | 40/20 | 1/20 | 1.5 | 328 | 4.1 | 0 | 1830 | 240 | GRAS. Relatively hard material and resistant to thermal and mechanical shock. Insoluble in water but can be attacked by strong acids and bases. |
| ZnSe | 15,000 | 461 508 |
2.40@10 | 40/20 | 1/20 | 1.2 | 219 | 5.3 | 0 | 1526 | 120 | Hard and brittle. Attacked by strong acids and bases. Resistance can be improved with the use of a hard coating. The most popular material for ATR applications. When AR coated, can be used as CO 2 laser window. |
| ZrO2 | 40,000 | 1431 | 2.13@1 | 60/40 | 1/8 | 1.1 | 5.9 | 0 | 2700 | 1250 | Hard material with good resistance to chemicals. Cannot be used at high temperatures as a phase change occurs at 1000 °C. |