High-temperature crystal structure and electronic properties of cesium niobate Cs2Nb4O11

The antiferroelectric material Cs2Nb4O11 transforms at 165 °C from a low-temperature, antiferroelectric phase in space group Pnna to a high-temperature, paraelectric phase in space group Imma; the latter structure has been determined by single-crystal X-ray diffraction. The high-temperature lattice is comprised of niobium-centered tetrahedra and octahedra connected through shared vertices and edges; cesium atoms occupy channels afforded by the three-dimensional polyhedral network. Calculated band structures for both phases predict a bandgap of 3.1–3.2 eV, which is similar to that found experimentally through photoluminescence. The calculated band structure is also conducive to its observed photocatalytic properties.