Caesium Iodide ( CsI ), Cesium Iodide - Properties and Applications


Caesium Iodide (CsI) is hygroscopic and readily dissolves in water. This property means that it needs to be kept away from water and also makes it difficult to polish.

Key Properties

Property Value
Density (g/cm3) 4.51
Melting Point (°C) 621
Young’s Modulus (GPa) 5.30
Dielectric Constant at 25 °C at 106 Hz 5.65
Co-Efficient of Thermal Expansion (m/m/°C at 20 °C) 39.1 x 10-6


Caesium Iodide is used to make cell windows and prisms for infrared application up to 50 µm.

It is also used in beam splitters for Fourier Transform Infra-Red (FTIR) devices. And in scintillators where it may or may not be doped with Thallium.


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