Cesium iodide (CsI:Tl) crystal is a scintillation crystal, which uses cesium iodide as the matrix material and is doped with an appropriate concentration of thallium (Tl). This crystal has a colorless and transparent cubic structure. CsI:Tl crystals belong to the halide scintillators and are characterized by high density, high average coefficient, low melting point, and high luminous efficiency.

When high-energy rays (such as X-rays and γ-rays) or other radioactive particles pass through such crystals, they are excited by the rays or particles, causing the crystals to emit a fluorescent pulse (scintillation light). This property makes them widely used in fields such as nuclear physics, nuclear medical imaging, geological exploration, industrial non-destructive testing, and security inspection. Especially in digital X-ray detectors, CsI:Tl scintillation crystals are widely used. With the positive development of the global digital X-ray detector market, the demand for CsI:Tl scintillation crystals is also increasing.

In addition, CsI:Tl crystals also possess advantages such as high light output, a good match between the light emission peak (550nm) and the sensitive region of silicon photodiodes, and resistance to deliquescence. Therefore, they are also used as scintillation materials in electromagnetic calorimeters and detectors in fields such as high-energy physics, security inspection, nuclear medical imaging, and geological exploration.

Regarding the production of CsI:Tl crystals, cesium iodide serves as the primary raw material, presenting as colorless or white crystals or crystalline powder. China boasts abundant rare earth resources, with a comprehensive range and substantial quantities of rare earth varieties. Notably, cesium resources are primarily located in the Altay region of Xinjiang and Yichun in Jiangxi. The growth methods for cesium iodide crystals typically encompass the Czochralski method, the vacuum descending method, and the non-vacuum descending method. Among these, the non-vacuum descending method is more commonly employed due to its lower production costs and higher production efficiency.