Metalloid nanocrystals may enable lithium-ion batteries to be replaced by more powerful sodium ion batteries. Tellurium, which is a semiconductor in its standard state, is used mainly as a component in type II/VI semiconducting-chalcogenides; these have applications in electro-optics and electronics. Cadmium telluride (CdTe) is used in solar modules for its high conversion efficiency, low manufacturing costs, and large band gap of 1.44 eV, letting it absorb a wide range of wavelengths. Bismuth telluride (BiTe), alloyed with selenium and antimony, is a component of thermoelectric devices used for refrigeration or portable power generation. Five metalloids—boron, silicon, germanium, arsenic, and antimony—can be
Antimony gangue minerals. Antimony can be isolated from the crude antimony sulfide by reduction with scrap iron: The sulfide is converted to an oxide; the product is then roasted, sometimes for the purpose of vaporizing the volatile antimony(III) oxide, which is recovered. This material is often used directly for the main applications, impurities being arsenic and sulfide. Antimony is isolated from the oxide by a carbothermal reduction: The lower-grade ores are reduced in blast furnaces while the higher-grade ores are reduced in reverberatory furnaces. Antimony has consistently been ranked high in European and US risk lists concerning criticality of the element