A Displacive-Type Metal Crown Ether Ferroelectric Compound: Ca(NO3)2(15-crown-5)

Following the Curie symmetry principle and Aizu rule, we discovered there is a centrosymmetric-to-noncentro-symmetric phase transition in Ca(NO3)2(15-crown-5) at T-c = 205 K. The transition was confirmed by differential scanning calorimetry and second harmonic generation measurements. The transition gives rise to excellent ferroelectricity, such as a giant dielectric anomaly, with faster polarization switching (5 x 10(-5) s) of up to 10(7) times without showing fatigue. The ferroelectric mechanism is attributable to the coordination environmental distortion of the central Ca atom. This finding can throw light on the further research in metal-organic ferroelectrics.