Ding Hui, Hadaeghi Niloofar, Zhang Mao-Hua, Jiang Tian-Shu, Zintler Alexander, Carstensen Leif, Zhang Yi-Xuan, Kleebe Hans-Joachim, Zhang Hong-Bin, Molina-Luna Leopoldo
Department of Materials and Earth Sciences, Technical University of Darmstadt, Darmstadt 64289, Germany.
ACS Appl Mater Interfaces. 2023 Dec 27;15(51):59964-59972. doi: 10.1021/acsami.3c15141. Epub 2023 Dec 12.
Planar defects are known to be of importance in affecting the functional properties of materials. Translational antiphase boundaries (APBs) in particular have attracted considerable attention in perovskite oxides, but little is known in lead-free antiferroelectric oxides that are promising candidates for energy storage applications. Here, we present a study of translational APBs in prototypical antiferroelectric NaNbO using aberration-corrected (scanning) transmission electron microscopy (TEM) techniques at different length scales. The translational APBs in NaNbO are characterized by a 2-fold-modulated structure, which is antipolar in nature and exhibits a high density, different from the polar nature and lower density in PbZrO. The high stability of translational APBs against external electric fields and elevated temperatures was revealed using ex situ and in situ TEM experiments and is expected to be associated with their antipolar nature. Density functional theory calculations demonstrate that translational APBs possess only slightly higher free energy than the antiferroelectric and ferroelectric phase energies with differences of 29 and 33 meV/f.u., respectively, justifying their coexistence down to the nanoscale at room temperature. These results provide a detailed atomistic elucidation of translational APBs in NaNbO with antipolar character and stability against external stimuli, establishing the basis of defect engineering of antiferroelectrics for energy storage devices.
平面缺陷在影响材料的功能特性方面具有重要意义。特别是平移反相界（APB）在钙钛矿氧化物中引起了相当大的关注，但在有望用于储能应用的无铅反铁电氧化物中却知之甚少。在此，我们使用不同长度尺度下的像差校正（扫描）透射电子显微镜（TEM）技术，对典型反铁电体NaNbO₃中的平移APB进行了研究。NaNbO₃中的平移APB具有2倍调制结构，本质上是反极性的，且密度较高，这与PbZrO₃中的极性本质和较低密度不同。通过非原位和原位TEM实验揭示了平移APB对外加电场和升高温度具有高稳定性，预计这与其反极性本质有关。密度泛函理论计算表明，平移APB的自由能仅比反铁电相和铁电相的能量略高，分别相差29和33 meV/f.u.，这证明了它们在室温下直至纳米尺度都能共存。这些结果对具有反极性特征且对外界刺激稳定的NaNbO₃中的平移APB进行了详细的原子层面阐释，为储能器件的反铁电体缺陷工程奠定了基础。
