Chapter 5: Heteroanionic Materials: The Structures and Applications of Mixed Anion Materials Check Access

In this chapter we discuss the structures, properties and applications of mixed anion materials—solid state compounds that contain at least two different anions directly co-ordinated to metal ions, which are also known as heteroanionic materials. We focus on the most common types found in the literature, materials containing two different anions of which one is oxide, and divide these into two classes dependant on the nature of the second anion. In the first type the oxide anion is paired with an isoelectronic ‘light’ anion such as oxide or fluoride. We use the widely investigated oxynitrides as a case study for this type, and explore their structures and applications as pigments and visible light photocatalysts. In the second type the oxide anion is paired with a ‘heavy anion’ from the third or fourth period of the periodic table, such as sulfide, selenide, phosphide or arsenide. We describe the structures adopted by these heavy anion containing materials, and highlight their properties by using the case studies of oxychalcogenides as p-type conductors and superconductivity in the oxyarsenides.