Product Description
Cesium iodide (CsI) — and thallium-doped CsI [CsI(Tl)] in particular — is an alkali halide scintillator widely deployed in high-energy particle detection and ionizing-radiation instrumentation. Thermally evaporated CsI(Tl) films were among the first scintillator materials adopted for X-ray imaging, coupled to photodiode-based readout systems.
In modern digital X-ray imaging, CsI(Tl) films remain the material of choice owing to their high X-ray-to-light conversion efficiency, a columnar microstructure that preserves spatial resolution, and a close spectral match to silicon photodiode arrays (a-Si, CMOS). Together, these properties deliver high-sensitivity, low-distortion imaging with fine diagnostic detail.
Product Parameters
| Melting point | 626 °C (lit.) |
| Boiling point | 1280 °C |
| density | 4.51 g/mL at 25 °C (lit.) |
| refractive index | 1.7876 |
| Fp | 1280°C |
| storage temp. | Keep in dark place,Inert atmosphere,Room temperature |
| solubility | soluble in ethanol, methanol, acetone |
| form | beads |
| Specific Gravity | 4.51 |
| color | White |
| PH | pH(50g/l, 25℃) : 5.0～9.0 |
| Water Solubility | 74 g/100 mL (20 ºC) |
| Sensitive | Hygroscopic |
| Merck | 142014 |
| Exposure limits | ACGIH: TWA 0.01 ppm |
| Dielectric constant | 5.6（Ambient） |
| Stability: | Stable. Deliquescent. |
| CAS DataBase Reference | 7789-17-5(CAS DataBase Reference) |
| NIST Chemistry Reference | Cesium iodide(7789-17-5) |
| EPA Substance Registry System | Cesium iodide (CsI) (7789-17-5) |
| Hazard Codes | Xn,Xi |
| Risk Statements | 36/37/38-42/43-43 |
| Safety Statements | 22-36/37-45 |
| RIDADR | UN 3077 9 / PGIII |
| WGK Germany | 2 |
| RTECS | FL0350000 |
| F | 8 |
| TSCA | Yes |
| HS Code | 28276000 |
| Toxicity | LD50 i.p. in rats: 1.4 g/kg (Cochran) |
Application Scenarios
CsI crystals are widely used as scintillator media in electromagnetic calorimeters for high-energy physics experiments. In addition, CsI optical crystals serve as transmission window substrates in Fourier-transform infrared (FT-IR) spectrometers, owing to their broad infrared transmission characteristics.
Compared with the more common potassium bromide (KBr) windows, CsI offers a wider spectral transmission range that extends further into the far-infrared region. However, CsI is relatively soft and lacks well-defined cleavage planes, which makes it more difficult to achieve a flat, high-quality optical polish.
CsI is also hygroscopic and must be stored under dry, desiccated conditions to prevent reaction with atmospheric moisture. Applying a thin germanium (Ge) protective coating to the optical surface effectively mitigates moisture-induced degradation during handling and window replacement.
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