Ferroelectricity and Related Properties of Nitratecadmate(II) Hybrid with Metal-Vacancy.

All crystals are not ideal, and many of their properties are often determined not by the regular arrangement of atoms, but by the irregular arrangement of crystal defects. Many properties of materials can be controlled effectively by proper use of solid defects. By substitution of NH ion of a hexagonal perovskite structure (H dabco)(NH )(NO ) (dabco=1,4-diazabicyclo[2.2.2]octane, 1) with Cd ion, we obtained a new metal-vacancy compound (H dabco) Cd(H O) (NO ) (2). It exhibits a ferroelectric-paraelectric phase transition at 261 K. A comparison of the various-temperature single-crystal structures indicates that the coordination twist of Cd ion leads to instability of the lattices and excellent ferroelectricity. These findings reveal that the vacancy can be utilized as an element to produce ferroelectricity and may start the chemistry of metal-vacancy coordination compounds. These findings reveals that the vacancy can be utilized as an effective means to tune the symmetry and produce ferroelectricity.