Цезий йодид

Химические свойства

white crystalline powder

Использование

Cesium iodide (CsI) is a kind of ionic compound that has been widely used as scintillators in many areas such as X-ray image intensifier tubes, photocathodes, and display devices.
Cesium iodide is used in scintillation counters(Geiger counters) to measure levels of external radiation. It is also useful as a "getter" to remove air molecules remaining in vacuum tubes.
Cesium Iodide is a material with high γ-ray stopping power due to its relative high density and atomic number. For scintillation counting, it is used either in its un-doped form or doped with sodium or thallium.
CsI is resistant to thermal and mechanical shock. The physical characteristics of CsI are independent of the activator used. Compared to NaI(Tl), it is relatively soft and plastic, and does not cleave. Because it has no cleavage plane, it is quite rugged-which makes it well-suited for well logging, space research or other applications where severe shock conditions are encountered.

Общее описание

Cesium iodide is a simple ionic salt. It has the capacity to undergo second order transformation from cubic B2 structure to body-centered tetragonal structure at low pressures. It is mostly used as input screens of X-ray image intensifiers.

Профиль безопасности

Moderately toxic by ingestion and intraperitoneal routes. See also CESIUM and IODIDES. When heated to decomposition, it emits toxic fumes of I-.

Синтез

The main method for preparing cesium iodide-based single crystals is Kyropoulos growth, which allows one to obtain cylindrical ingots weighing up to several tens of kilograms.
Cs2CO3+ 2HI→2CsI+H2O+CO2↑
Technically, pure CsI was prepared by dissolving cesium carbonate in hydriodic acid at room temperature in a vessel from niobium, which was nonreactive with cesium iodide at elevated temperatures. The solution was heated to boiling at pH 3 to completely dissolve the caesium carbonate because the niobium vessel was unstable in an acid medium.The hot solution was filtered and boiled down at a temperature near 393 K. After crystallization, the material was vacuum-dried in a quartz ampule[4].

Методы очистки

Crystallise it from warm water (1mL/g) by cooling to -5o.

Структура и конформация

The space lattice of CsI belongs to the cubic system, and its cesium chloride structure has a lattice constant of a=0.8529 nm.