oxyselenides

Oxyselenides are a class of inorganic compounds that contain both oxide (O2−) and selenide (Se2−) anions in combination with metal cations. They are a subset of mixed-anion chalcogenides and are often characterized by layered structures that combine oxide and selenide layers, yielding anisotropic physical properties.

Typical members include lanthanide oxyselenides with the formula Ln2O2Se (where Ln represents a lanthanide such as La, Ce, Pr, Nd, Sm, etc.) and bismuth-based oxyselenides such as Bi2O2Se. These materials commonly feature alternating oxide and selenide layers coordinated by cationic sheets, with the exact arrangement depending on composition. Substitution on either the lanthanide or transition-metal site, as well as chalcogenide substitution, can modify the electronic structure and lattice parameters, enabling tuning of properties.

Synthesis of oxyselenides generally involves high-temperature solid-state reactions starting from oxides, selenides, or related precursors, often under inert or reducing conditions to control selenium volatility. Methods to obtain single crystals include flux growth and, for some systems, chemical vapor transport. Some members are readily prepared as polycrystalline powders, while others require carefully controlled conditions to stabilize particular polymorphs or layered motifs.

Properties of oxyselenides are diverse. They are typically semiconductors with optoelectronic and thermoelectric potential, and their layered architecture can lead to strong anisotropy in electrical and thermal transport. Lanthanide-containing oxyselenides may exhibit magnetic ordering from localized f-electrons, while Bi2O2Se-type compounds are explored for their narrow-band semiconducting behavior and thermoelectric performance. Ongoing research focuses on discovering new compositions, understanding structure–property relationships, and exploring potential applications in energy and electronics.