Thallium bromide iodide (KRS-5) is an optical crystal made from a mixture of thallium bromide and thallium iodide crystals and is an ideal infrared material often used in the infrared spectrum for attenuated total reflection prisms, lenses and windows. Alfa Chemistry can custom fabricate optical components of virtually any shape and size to customer requirements using KRS-5 material. If you need assistance, please contact us.
Advantages and Uses of Thallium Bromo-Iodide Materials
KRS-5 is a deep infrared material with a high refractive index. KRS-5 material can transmit an infrared wavelength range from 0.5 to 40 µm and is non-hygroscopic, making it particularly effective in the air. Additionally, it can transmit up to 70% or more. From the red visible spectrum (0.6 µm) to the far infrared spectrum (50 µm), the KRS-5 material is transparent throughout a broad spectral range. When transmittance between 0.6 and 40 µm is necessary, KRS-5 prisms, IR KRS-5 windows, and KRS-5 lenses are made of the KRS-5 crystal material. When combined with germanium, KRS-5 can also be used in non-thermal infrared imaging systems.
Fig 1. Measured transmittance of 2 mm-thick KRS-5 and KRS-6 samples in the visible and near infrared spectral ranges. The inset shows photos of these materials. (Marcinkevičiūtė A, et al. 2018)
KRS-5 crystal materials are crystallized by the Stockbarger technique. The KRS-5 material has a tendency to cold flow and change shape over time. KRS-5 crystals are only slightly soluble in water but are soluble in alcohol, nitric acid, and aqua regia.
Properties of Thallium Bromo-Iodide Materials
| Density | 7.371 g/cc |
| Molecular Weight | 42 mole% TlBr; 58 mole% TlI |
| Solubility | 0.05g/100g water at 293K |
| Class/Structure | Cubic, CsCl structure, Pm3m, No cleavage |
| Melting Point | 414.5 °C |
| Hardness | Knoop 40.2 |
| Refractive Index | 2.371 at 10 μm |
| Transmission Range | 0.6 to 40 μm |
| Reflection Loss | 28.4% at 10 μm (2 surfaces) |
| Apparent Elastic Limit | Cubic, CsCl structure, Pm3m, No cleavage |
| dn/dT | -235 x 10-6 /°C |
| Youngs Modulus (E) | 15.85 GPa |
| Shear Modulus (G) | 5.79 GPa |
| Bulk Modulus (K) | 19.78 GPa |
| Thermal Expansion | 58 x 10-6 /°C |
| Thermal Conductivity | 0.544 W/m/K at 293K |
| Dielectric Constant | 32.5 |
| Specific Heat Capacity | 200 J Kg-1 K-1 at 273K |
| Poisson Ratio | 0.369 |
| Elastic Coefficients | C11=331; C12=13.2; C44=5.79 |
About refractive index parameters.
"No" means ordinary light.
| µm | No | µm | No | µm | No |
|---|---|---|---|---|---|
| 0.54 | 2.68059 | 1.00 | 2.4462 | 1.50 | 2.40774 |
| 2.00 | 2.39498 | 3.00 | 2.38574 | 4.00 | 2.38204 |
| 5.00 | 2.37979 | 6.00 | 2.37797 | 7.00 | 2.37627 |
| 8.00 | 2.37452 | 9.00 | 2.37267 | 10.00 | 2.37069 |
| 11.00 | 2.36854 | 12.00 | 2.36622 | 13.00 | 2.36371 |
| 14.00 | 2.36101 | 15.00 | 2.35812 | 16.00 | 2.35502 |
| 17.00 | 2.35173 | 18.00 | 2.34822 | 19.00 | 2.34451 |
| 20.00 | 2.34058 | 21.00 | 2.33643 | 22.00 | 2.33206 |
| 23.00 | 2.32746 | 24.00 | 2.32264 | 25.00 | 2.31758 |
| 26.00 | 2.31229 | 27.00 | 2.30676 | 28.00 | 2.30098 |
| 29.00 | 2.29495 | 30.00 | 2.28867 | 31.00 | 2.28212 |
| 32.00 | 2.27531 | 33.00 | 2.26823 | 34.00 | 2.26087 |
| 35.00 | 2.25322 | 36.00 | 2.24528 | 37.00 | 2.23705 |
| 38.00 | 2.2285 | 39.00 | 2.21965 | 40.00 | 2.21047 |
Reference
- Marcinkevičiūtė A, et al. (2018). "Supercontinuum Generation in Mixed Thallous Halides KRS-5 and KRS-6." Optical Materials. 78: 339-344.