Achieving High Dielectric Constant Relaxor Ferroelectric Nanocrystals via a Hybridization-Induced Nanodomain Approach

摘要：纳米结构铁电材料在未来的微纳米电子应用中显示出巨大的潜力，包括用于人体监测的可穿戴医疗传感器、非易失性铁电存储器、压电/电致伸缩驱动、二次谐波成像、能量收集和存储、电热冷却和液晶显示。不幸的是，当铁电材料的尺寸减小到几十纳米时，由于铁电相的不稳定，它们的高介电性能最终会消失。因此，开发具有稳定铁电相和纳米结构域的新型高介电常数铁电纳米晶体是迫切需要的。对无机纳米晶体中聚合物缺陷诱导的铁电纳米畴的理解为创造许多其他有趣的铁电纳米晶体铺平了道路。同时，该研究项目与纳米科学教育相结合，通过研究生、本科生、高中科学教师和高中生之间的密切互动，在乔治亚理工学院和凯斯西储大学发现的兴奋的启发下，提供多层次的学习体验。其目标是激发高中生对科学、技术、工程和数学（STEM）领域的兴趣，并更好地为本科生从事STEM相关职业做好准备。为了提高公众对纳米科学和纳米技术的认识，研究成果通过在科学期刊上发表文章、在国家会议和研讨会上发表演讲等方式广泛传播给多个领域。技术摘要：本研究旨在了解有机/无机杂化对聚合物系链杂化BaTiO3纳米晶体中纳米级铁电相和畴结构的影响，并将其潜在机制扩展到其他无铅弛豫铁电体系中，以实现各种潜在电应用的高介电常数。首先，合理设计合成了新型两亲性非线性嵌段共聚物。随后，采用两亲性非线性嵌段共聚物作为纳米反应器，制备了具有精确定制尺寸的均匀聚合物系缚杂化BaTiO3纳米晶体。利用高分辨率透射电子显微镜研究了聚合物系链杂化BaTiO3纳米晶体的纳米级铁电相和畴结构，揭示了其弛豫铁电行为的机制。最后，将基本机制扩展到具有更高介电常数的其他无铅弛豫铁电纳米晶体。

Nontechnical Abstract:Nanostructured ferroelectric materials show great potential for future micro- and nano-electronic applications, including wearable medical sensors for human monitoring, non-volatile ferroelectric memory, piezoelectric/electrostrictive actuation, second harmonic generation imaging, energy harvesting and storage, electrocaloric cooling, and liquid crystal displays. Unfortunately, as the dimensions of ferroelectric materials decrease to a few tens of nanometers, their high dielectric property eventually disappears as a result of destabilization of the ferroelectric phase. Therefore, it is highly desirable to develop novel, high dielectric constant ferroelectric nanocrystals with stable ferroelectric phase and nanosized domains. The understanding of polymer defect-induced ferroelectric nanodomains within inorganic nanocrystals paves the way to create many other intriguing ferroelectric nanocrystals. Meanwhile, the research project is integrated with nanoscience education through close interactions among graduate students, undergraduate students, high school science teachers, and high school students in a multilevel learning experience inspired by the excitement of discovery at both Georgia Tech and Case Western Reserve University. The goals are to stimulate the interest of high school students in the area of science, technology, engineering, and mathematics (STEM), and better prepare undergraduate students for the STEM-related professions. To enhance the public awareness of nanoscience and nanotechnology, research findings are widely disseminated to multiple constituencies through publications in scientific journals, presentations at national conferences and workshops.Technical Abstract:This proposal aims to understand the effect of organic/inorganic hybridization on the nanoscopic ferroelectric phase and domain structures in polymer-tethered hybrid BaTiO3 nanocrystals, and extend the underlying mechanism to other lead-free relaxor ferroelectric systems to achieve high dielectric constants for various potential electrical applications. First, novel amphiphilic nonlinear block copolymers are rationally designed and synthesized. Subsequently, uniform polymer-tethered hybrid BaTiO3 nanocrystals with precisely tailored dimensions are crafted by employing amphiphilic nonlinear block copolymers as nanoreactors. The nanoscale ferroelectric phase and domain structures in polymer-tethered hybrid BaTiO3 nanocrystals are interrogated using high-resolution transmission electron microscopy, and the mechanism of their relaxor ferroelectric behavior can be unraveled. Finally, the underlying mechanism are extended to create other lead-free relaxor ferroelectric nanocrystals with even higher dielectric constants.