Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit

Wenru Li¹, Gang Tang², Guangzu Zhang³, Hasnain Mehdi Jafri⁴, Jun Zhou¹, Di Liu⁴, Yang Liu⁵, Jiesu Wang⁶, Kuijuan Jin⁶, Yongmin Hu⁷, Haoshuang Gu⁷, Zhao Wang⁷, Jiawang Hong⁸, Houbing Huang⁹, Long-Qing Chen⁵, Shenglin Jiang¹, Qing Wang¹⁰

Affiliations

¹ School of Optical and Electronic Information, and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China.
² School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China.
³ School of Optical and Electronic Information, and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
⁴ School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
⁵ Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA.
⁶ Institute of Physics, Chinese Academy of Sciences, Beijing, China.
⁷ Hubei Key Laboratory of Ferro- & Piezoelectric Materials and Devices, Faculty of Physics and Electronic Science, Hubei University, Wuhan, Hubei, China.
⁸ School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
⁹ School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
¹⁰ Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.

PMID: 33514555
PMCID: PMC7846162
DOI: 10.1126/sciadv.abe3068

Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit

Wenru Li et al. Sci Adv. 2021.

. 2021 Jan 29;7(5):eabe3068.

doi: 10.1126/sciadv.abe3068. Print 2021 Jan.

Authors

Affiliations

¹ School of Optical and Electronic Information, and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China.
² School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China.
³ School of Optical and Electronic Information, and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
⁴ School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
⁵ Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA.
⁶ Institute of Physics, Chinese Academy of Sciences, Beijing, China.
⁷ Hubei Key Laboratory of Ferro- & Piezoelectric Materials and Devices, Faculty of Physics and Electronic Science, Hubei University, Wuhan, Hubei, China.
⁸ School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
⁹ School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.
¹⁰ Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA. zhanggz@hust.edu.cn hongjw@bit.edu.cn hbhuang@ustb.edu.cn wang@matse.psu.edu.

PMID: 33514555
PMCID: PMC7846162
DOI: 10.1126/sciadv.abe3068

Abstract

Although ferroelectric materials exhibit large pyroelectric coefficients, their pyroelectric figures of merit (FOMs) are severely limited by their high dielectric constants because of the inverse relationship between FOMs and dielectric constant. Here, we report the molecular ferroelectric [Hdabco]ClO₄ and [Hdabco]BF₄ (dabco = diazabicyclo[2.2.2]octane) exhibiting improper ferroelectric behavior and pyroelectric FOMs outperforming the current ferroelectrics. Concurrently, the improper molecular ferroelectrics have pyroelectric coefficients that are more than one order of magnitude greater than the state-of-the-art pyroelectric Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ Our first-principles and thermodynamic calculations show that the strong coupling between the order parameters, i.e., the rotation angle of anions and polarization, is responsible for the colossal pyroelectric coefficient of the molecular ferroelectrics. Along with the facile preparation and self-poling features, the improper molecular ferroelectrics hold great promise for high-performance pyroelectric devices.

Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

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Figures

**Fig. 1. XRD patterns and molecular structure of [Hdabco]ClO₄.**
XRD patterns of (A) orthorhombic and (B) tetragonal phases of [Hdabco]ClO₄ along with the simulated results. a.u., arbitrary units. The molecular structures of (C and E) orthorhombic and (D and F) tetrahedral phases viewed along the different directions. The dihedral angle θ is the angle between the plane composed of three oxygen atoms and the ab plane, and the ionic displacement δ is the one between the centers of [Hdabco]⁺ cation and [ClO₄]⁻ anion along the b axis.

**Fig. 2. The dielectric, ferroelectric, and pyroelectric properties of [Hdabco]ClO₄.**
(A) Dielectric constant (ε_r) and loss tangent (tanδ) of [Hdabco]ClO₄ as a function of temperature. (B) Polarization-field (P-E) loops of [Hdabco]ClO₄ measured at 100 Hz and different temperatures. (C) Spontaneous polarization (P_S) as a function of temperature. A marked drop is observed at 378 K, corresponding to the Curie phase transition. (D) Temperature-dependent pyroelectric coefficient (p). (E) Voltage responsivity (F_V). (F) Detectivity (F_D). (G) FOM of energy harvesting (F_E).

**Fig. 3. The pyroelectric coefficients and dielectric constants of pyroelectric materials.**
PbZrO₃ (15), PbTiO₃ (15), PbZr_0.3Ti_0.7O₃ (18), 0.7Pb(Mg_1/3Nb_2/3)O₃–0.3PbTiO₃ (4), LiTaO₃ (5), LiNbO₃ (2), Sr_0.5Ba_0.5Nb₂O₆ (45), BaCe_0.12Ti_0.88O₃ (46), Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (9), PVDF (1), P(VDF/TrFE)50/50 (6), and P(VDF/TrFE)56/44 (47).

**Fig. 4. The experimental and calculated spontaneous polarization of [Hdabco]ClO₄ and [Hdabco]BF₄.**
(A) Comparison of the experimental and simulated temperature-dependent P_S of [Hdabco]ClO₄ and [Hdabco]BF₄. The plots are the experimental data, and the solid lines are the calculated results. (B) Relation between the spontaneous polarization of [Hdabco]ClO₄ and [Hdabco]BF₄ and the rotation angle. The stepper slop of [Hdabco]ClO₄ indicates its stronger coupling between the polarization and θ than that of [Hdabco]BF₄.

See this image and copyright information in PMC

References

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1. Lang S. B., Pyroelectricity: From ancient curiosity to modern imaging tool. Phys. Today 58, 31–36 (2005).
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Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit

Affiliations

Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit

Authors

Affiliations

Abstract

Figures

References

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