chalcogenides

Chalcogenides are chemical compounds that contain at least one chalcogen atom—oxygen, sulfur, selenium, tellurium, or polonium—in combination with another element. The term covers a broad family, including oxides, sulfides, selenides, tellurides, and polonides, and spans simple binary species such as metal sulfides as well as more complex compounds. They occur widely in minerals and are prepared intentionally for electronic, catalytic, and energy applications.

Bonding in chalcogenides ranges from predominantly ionic in many metal chalcogenides to covalent or metallic in others. A prominent subgroup is transition metal dichalcogenides (MX2, with M a transition metal and X S, Se, or Te), which adopt layered structures with weak interlayer interactions. This enables exfoliation to two-dimensional sheets with unique electronic and optical properties. Oxide chalcogenides form a large class of ceramics and semiconductors.

In nature, sulfide minerals such as pyrite (FeS2) and galena (PbS), and oxide minerals such as corundum (Al2O3) and hematite (Fe2O3) illustrate the scope of chalcogenides. Synthetic routes include solid-state synthesis, chemical vapor deposition, hydrothermal methods, and solution-based processing, often tailored to achieve particular crystal structures and stoichiometries.

Chalcogenides have diverse applications. They are important in electronics and photovoltaics (for example, CdS, CdTe, and Cu(In,Ga)Se2 solar cells), thermoelectrics (Bi2Te3, PbTe, SnSe), and catalysis (molybdenum disulfide for hydrogen evolution). They also serve as battery and supercapacitor materials and as functional layers in optoelectronic devices and sensors.

Safety and environmental considerations vary by composition. Some sulfides and tellurides involve toxic elements or sulfide dusts, and proper handling and disposal are required in industrial use and mining.