Cesium iodide (CsI) is an IR transmitting material suitable for components in the widest range of spectrophotometers. Thallium-doped CsI(Tl) is a useful scintillator with an emission wavelength that closely matches that of silicon photodiodes. CsI arrays, a crucial optical component, are frequently employed in security imaging systems. In accordance with customer specifications, Alfa Chemistry can custom-manufacture optical components out of CsI materials, such as CsI windows, CsI lenses, and CsI prisms, in almost any size and shape. Please get in touch with us if you require assistance.
Advantages and Uses of Caesium Iodide Materials
The material Csl is water soluble and transmits light from the ultraviolet (0.25 µm) to the far infrared (55 µm). with a transmittance of over 80% between 0.40-40 µm, Csl has the widest transmission band of any widely available IR material. Although the material is extremely resilient to shock and abrupt temperature fluctuations, it may deteriorate in air circumstances. We therefore strongly advise using a protective coating, which normally consists of a broadband anti-reflective coating and a moisture resistant anti-reflective coating for material exposure. Csl is an extremely soft material with a hardness of HK20 and is difficult to polish, so performance can be compromised by range.
Fig 1. The transmittance of cesium iodide. (Plyler E. K, et al. 1958)
Typical applications include imaging systems, analytical instruments, components for infrared spectroscopy and Fourier Transform Infrared (FTIR) instruments, and numerous uses in medical instrumentation. FTIR spectrometers use Csl as a beam splitter. Operating in the far infrared, Csl offers a larger transmission range than the more popular potassium bromide beam splitter. When thallium is added to Csl, it transforms into a useful scintillator with an emission range similar to that of a silicon photodiode. It is a good detector of high energy particles as a result. Csl is frequently employed in medicine as a scintillation material in flat panel x-ray detectors in addition to being image intensifier input phosphors.
Properties of Caesium Iodide Materials
| Density | 4.51 g/cc |
| Molecular Weight | 259.83 |
| Solubility | 44 g/100 g water at 0 °C |
| Class/Structure | Cubic CsCl, Pm3m, no cleavage, deforms |
| Melting Point | 621 °C |
| Hardness | Knoop 20 with 200g indenter |
| Refractive Index | 1.73916 at 10 μm |
| Transmission Range | 0.25 to 55 μm |
| Reflection Loss | 13.6% at 10 μm |
| Apparent Elastic Limit | 5.6 MPa (810psi) |
| dn/dT | -99.3x10-6 /°C |
| Youngs Modulus (E) | 5.3 GPa |
| Shear Modulus (G) | 6.24 GPa |
| Bulk Modulus (K) | 12.67 GPa |
| Thermal Expansion | 48.3x10-6 /°C at 293 K |
| Thermal Conductivity | 1.1 W/m/K at 298 K |
| Dielectric Constant | 5.65 at 1 MHz |
| Specific Heat Capacity | 201 J Kg-1 K-1 |
| Poisson Ratio | 0.214 |
| Elastic Coefficients | C11=24.6 C126.7 C44=6.24 |
| Reststrahlen Peak | 145.8 μm |
About refractive index parameters.
"No" means ordinary light.
| µm | No | µm | No | µm | No |
|---|---|---|---|---|---|
| 0.5 | 1.8064 | 1.0 | 1.7572 | 2.0 | 1.7466 |
| 3.0 | 1.7440 | 4.0 | 1.7431 | 5.0 | 1.7424 |
| 6.0 | 1.7418 | 7.0 | 1.7412 | 8.0 | 1.7406 |
| 9.0 | 1.7399 | 10.0 | 1.7392 | 11.0 | 1.7384 |
| 12.0 | 1.7375 | 13.0 | 1.7365 | 14.0 | 1.7355 |
| 15.0 | 1.7344 | 16.0 | 1.7332 | 17.0 | 1.7319 |
| 18.0 | 1.7306 | 19.0 | 1.7291 | 20.0 | 1.7276 |
| 21.0 | 1.7260 | 22.0 | 1.7244 | 23.0 | 1.7226 |
| 24.0 | 1.7207 | 25.0 | 1.7188 | 26.0 | 1.7168 |
| 27.0 | 1.7147 | 28.0 | 1.7125 | 29.0 | 1.7101 |
| 30.0 | 1.7077 | 31.0 | 1.7052 | 32.0 | 1.7027 |
| 33.0 | 1.7000 | 34.0 | 1.6972 | 35.0 | 1.6943 |
| 36.0 | 1.6913 | 37.0 | 1.6882 | 38.0 | 1.6849 |
| 39.0 | 1.6816 | 40.0 | 1.6781 | 41.0 | 1.6746 |
| 42.0 | 1.6709 | 43.0 | 1.6671 | 44.0 | 1.6631 |
| 45.0 | 1.6591 | 46.0 | 1.6549 | 47.0 | 1.6505 |
| 48.0 | 1.6460 | 49.0 | 1.6414 | 50.0 | 1.6366 |
Reference
- Plyler E. K, et al. (1958). "Transmittance and Reflectance of Cesium Iodide in the Far Infrared Region." Journal of the Optical Society of America. 48(9): 668-669.