Improper Ferroelectricity in Stuffed Aluminate Sodalites for Pyroelectric Energy Harvesting

Abstract

Ferroelectricity in stuffed aluminate sodalites, (Ca1−xSrx)8[AlO2]12(WO4)2 (x ≤ 0.2) (C1−xSxAW), is demonstrated in the present study. Pyroelectric measurements clarified switchable spontaneous polarization in polycrystalline C1−xSxAW, whose polarization values were on the order of 10 −2 C/cm 2 at room temperature. A weak anomaly in the dielectric permittivity at temperatures near the ferroelectric transition temperature suggested 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 clarified that the ferroelectric phase transition of C1−xSxAW is driven by 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.

Improper ferroelectrics as high‐efficiency energy conversion materials

“…This value is similar to previously reported values for improper ferroelectrics . Given the small P s and the weak dielectric anomaly discussed in the preceding paragraph, we concluded that CSAM‐16 is an improper ferroelectric material as in the case of (Ca 1 −x Sr x ) 8 [AlO 2 ] 12 (WO 4 ) 2 .…”

Hybrid Improper Ferroelectricity in (Sr,Ca)3Sn2O7 and Beyond: Universal Relationship between Ferroelectric Transition Temperature and Tolerance Factor in n = 2 Ruddlesden–Popper Phases

“…This relationship provides a predictive guideline for estimating T C of a given material, which would complement the design approach based on group theory and first principles. Further, the findings open routes to the possible use of hybrid improper ferroelectrics in technological applications: for example, pyroelectric energy harvesting [83][84][85] , where the tunability of T C is advantageous for achieving a large electrothermal coupling factor.…”

Energy Harvesting Research: The Road from Single Source to Multisource

“…All these materials perform better than conventional PZT‐5H (a type of soft PZT). The lead‐free compositions such as LiNbO 3 , CSBN (Ca 0.15 (Sr 0.5 Ba 0.5 ) 0.85 Nb 2 O 5 ), CSAW ((Ca 1− x Sr x ) 8 (AlO 2 ) 12 WO 4 ), and BTO based and BNT‐BTO based are not necessarily better than PZT for pyroelectric energy conversion, but they are better than conventional lead‐free counterparts, e.g., ZnO. PZT with aligned porosity proved to have a substantial increase in energy density compared to dense PZT .…”