Oxidephosphates

Oxidephosphates are inorganic compounds that contain both oxide (O2−) ions and phosphate (PO4^3−) groups within a single solid. They form mixed-anion materials in which phosphate tetrahedra connect to metal-oxide polyhedra, creating diverse networks. Structures range from three-dimensional frameworks to layered or chain-like motifs, depending on composition and synthesis. The combination of oxide and phosphate components often yields properties distinct from pure oxides or phosphates.

Synthesis and structure: Oxidephosphates are produced by solid-state reactions or solution-based methods from metal oxides, phosphates, and phosphoric acid derivatives, as well as by hydrothermal or glass-forming routes. The motifs typically feature PO4 tetrahedra sharing oxygen with metal-oxygen units, forming networks that accommodate various cations and oxidation states. Oxide content can influence density, stability, and connectivity of the framework.

Properties and applications: Mixed-anion networks can impart hardness and chemical durability, alongside functional traits such as ionic conduction (oxide-ion or proton conductors) and luminescence when doped with lanthanides or transition metals. Oxidephosphates appear in ceramics, glass-ceramics, catalysts, and solid-state electrolytes, and are studied for waste immobilization and as precursors to more complex oxide-phosphate systems.

Examples and scope: The field includes rare-earth and transition-metal oxyphosphates and related mixed-anion compounds. The term oxidephosphate is used for materials that integrate oxide ions into phosphate-rich networks, reflecting a broader category within mixed-anion chemistry.