Journal Article Improper Ferroelectricity in Stuffed Aluminate Sodalites for Pyroelectric Energy Harvesting

Maeda, Yusaku  ,  Wakamatsu, Toru  ,  Konishi, Ayako  ,  Moriwake, Hiroki  ,  Moriyoshi, Chikako  ,  Kuroiwa, Yoshihiro  ,  Tanabe, Kenji  ,  Terasaki, Ichiro  ,  Taniguchi, Hiroki

7 ( 3 )  , pp.034012 - 034012 , 2017-03-24 , American Physical Society
In the present study, we demonstrate ferroelectricity in stuffed aluminate sodalites (Ca1−xSrx)8[AlO2]12(WO4)2 (x≤0.2) (C1−xSxAW). Pyroelectric measurements clarify switchable spontaneous polarization in polycrystalline C1−xSxAW, whose polarization values are on the order of 10^−2  μC/cm^2 at room temperature. A weak anomaly in the dielectric permittivity at temperatures near the ferroelectric transition temperature suggests improper ferroelectricity of C1−xSxAW for all investigated values of x. A comprehensive study involving synchrotron x-ray powder diffraction measurements, molecular dynamics simulations, and first-principles calculations clarifies that the ferroelectric phase transition of C1−xSxAW is driven by the freezing of the fluctuations of WO4 tetrahedra in the voids of an [AlO2]12^12− framework. The voltage response and electromechanical coupling factor of C1−xSxAW estimated from the present results indicate that this material exhibits excellent performance as a pyroelectric energy harvester, suggesting that aluminate sodalites exhibit great promise as a class of materials for highly efficient energy-harvesting devices.

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