Precise Molecular Design Toward Organic–Inorganic Zinc Chloride ABX3 Ferroelectrics

Organic–inorganic
ABX3 (A, B = cations, X = anion)
hybrids with perovskite structure have recently attracted tremendous
interest due to their structural tunability and rich functional properties,
such as ferroelectricity. However, ABX3 hybrid ferroelectrics
with other structures have rarely been reported. Here, we successfully
designed an ABX3 hybrid ferroelectric [(CH3)3NCH2F]­ZnCl3 with a spontaneous polarization
of 4.8 μC/cm2 by the molecular modification of [(CH3)4N]­ZnCl3 through hydrogen/halogen substitution.
It is the first zinc halide ABX3 ferroelectric, which contains
one-dimensional [ZnCl3]−n chains of corner-sharing ZnCl4 tetrahedra,
distinct from the anionic framework of corner-sharing or face-sharing
BX6 octahedra in the ABX3 perovskites. From
zero dimension to one dimension, the high symmetry of ZnCl4 tetrahedra is broken, and all of them align along one direction
to form a polar [ZnCl3]−n chain, beneficial to the generation of ferroelectricity.
This finding provides an efficient polar anionic framework for enriching
the family of hybrid ferroelectrics by assembling with various cations
and should inspire further exploration of new classes of organic–inorganic
ABX3 ferroelectrics.

有机-无机杂化ABX3（A、B为阳离子，X为阴离子）钙钛矿结构材料近期因其在结构可调性及丰富的功能性特性（如铁电性）而受到广泛关注。然而，具有其他结构的ABX3杂化铁电材料鲜有报道。本研究中，我们通过[(CH3)3NCH2F]­ZnCl3的分子改性，即通过氢/卤素取代，成功设计了一种具有自发极化4.8 μC/cm2的ABX3杂化铁电材料。该材料为锌卤化物ABX3铁电材料中的首次出现，其中包含了一维的[ZnCl3]−n链，由角共享的ZnCl4四面体构成，与ABX3钙钛矿中角共享或面共享的BX6八面体阴离子框架截然不同。从零维到一维，ZnCl4四面体的高对称性被打破，并沿一个方向排列形成极性[ZnCl3]−n链，有利于铁电性的产生。这一发现为通过组装各种阳离子高效构建极性阴离子框架提供了途径，并应激发对新型有机-无机ABX3铁电材料的进一步探索。