Alkaliantimonides

Alkaliantimonides are binary inorganic compounds formed between alkali metals (such as lithium, sodium, potassium, rubidium, and cesium) and antimony. In these compounds, antimony is present as the Sb3− anion and the alkali metal ions balance the charge, giving stoichiometries commonly written as M3Sb (for M = Li, Na, K, Rb, Cs). Representative members include Na3Sb, K3Sb, Rb3Sb, Cs3Sb, and Li3Sb. Among these, Cs3Sb is the most extensively studied due to its optoelectronic properties.

Synthesis and structure often involve direct combination of the alkali metal with elemental antimony under strongly inert conditions and elevated temperature. The resulting solids are typically ionic and display crystal structures that vary with the specific alkali cation. They are generally sensitive to air and moisture, requiring handling under inert atmosphere to preserve phase purity.

Properties and reactivity: alkaliantimonides are reactive and can decompose in the presence of moisture or oxygen. Contact with water can yield hydrogen gas and stibine (SbH3), a highly toxic gas, making careful, closed-environment handling essential. They tend to be poor conductors in air and exhibit semiconducting behavior characteristic of many antimonide materials, with properties strongly influenced by the size of the alkali cation.

Applications: Cs3Sb, in particular, is notable as a photocathode material for visible-light detection in photomultiplier tubes and electron guns. The class as a whole is of interest in solid-state chemistry and materials science for understanding alkali–pnictide bonding and as precursors to Sb-containing functional materials.

Safety: due to toxicity of antimony compounds and potential release of SbH3 on moisture exposure, handling requires appropriate engineering controls and inert-atmosphere techniques.