弛豫铁电单晶多尺度极性结构及其协同效应研究

The manipulation of micro-structures, macro-properties and their correlation mechanism of relaxor ferroelectric single crystals has been a hot topic in the field of condense matter and material science. The present proposal is intended to investigate the multi-scale polar structures of Mn-doped PMN-PT and PIN-PMN-PT, i.e., defect dipole pair, polar nano region (PNR), domain structure and phase structure by synchrotron radiation, high resolution transmission electron microscope, neutron diffuse scattering, etc., and the cross-scale synergistic effects between defect dipole pair-PNR, defect dipole pair-phase structure. Four major issues will be addressed, including to: 1) experimentally observe the characteristics of multi-scale polar structures; 2) clarify evolution law of multi-scale polar structures in response to external physical fields; 3) develop methods for manipulation of multi-scale polar structures and properties; 4) reveal the underlying mechanism of cross-scale synergistic effect and the interaction of defect dipole pair-PNR, defect dipole pair-phase structure. This proposal will be mainly carried out in experiments, while simultaneously performed by some thermodynamic calculations and field phase modeling, in order to establish the physical link of “post-treatment process, configuration of multi-scale polar structure and macroscopic property”, and comprehensively study the manipulation of multi-scale polar structures and their interaction induced emergent phenomenon. This research and the promising results will not only deepen the connotation and extend the denotation of multi-scale polar heterogeneity of complex perovskites, but also provide physical basis to develop post-treatment process for properties optimization of relaxor ferroelectric single crystals and the related electronic device applications.

弛豫铁电单晶微观结构与宏观性能的调控及其关联机制一直是凝聚态物理和材料学科领域的研究热点。本项目以Mn掺杂弛豫铁电单晶为对象，拟采用同步辐射、中子散射等手段开展多尺度极性结构及“缺陷偶极-极性纳米微区”和“缺陷偶极-相结构”跨尺度协同效应的研究。研究内容主要包括:1)实验观察多尺度极性结构特征；2)明确多尺度极性结构的外物理场演变规律；3)发展多尺度极性结构与性能调控方法；4)揭示“缺陷偶极-极性纳米微区”和“缺陷偶极-相结构”跨尺度协同效应及机理。项目开展以实验探索为重点，以构筑“后处理工艺-多尺度极性结构组态-宏观性能增益”的物理图像为主线，结合热力学和相场模拟，对多尺度极性结构的调控及其协同衍生的新奇物理效应进行深入研究。该项目研究不仅可以拓展复杂钙钛矿氧化物多尺度不均匀性结构和跨尺度协同效应的物理内涵，也为发展弛豫铁电单晶性能优化的后处理工艺以及电子器件应用奠定物理基础。

复杂钙钛矿材料的多尺度极性结构的研究不仅能丰富和深化凝聚态物理学科自身的内涵，也为发展弛豫铁电单晶性能优化的后处理工艺以及电子器件应用奠定物理基础。在本项目的支持下，揭示了“缺陷偶极-极性纳米微区”和“缺陷偶极-相结构”跨尺度协同效应及机理，构筑了“后处理工艺-多尺度极性结构组态-宏观性能增益”的物理图像。取得的重要结果如下：.1）在[001]取向的 NBT-6BT-2KNN单晶中，获得了高达0.9%的可逆场致应变，揭示了[001]取向的 NBT-6BT-2KNN单晶在电场作用下的相结构演变规律；.2）在[001]取向的 NBT-6BT-KNN 单晶中，获得了目前报道最大的压电性能d33~840 pC/N，微结构分析揭示了极化后的单晶R3c和P4mm 共存，证实了高压电性能来源于电场诱导的R3c和P4mm相界，三元组分设计提升了P4mm相含量。同时，揭示了NBT-6BT-KNN单晶中存在跨尺度的畴结构，包括亚微米的铁弹畴和几到几十纳米尺度的弱极性铁电畴，其弛豫特性来源于纳米尺度的R3c弱极性铁电微区。.3）通过传统固相法设计制备了稀土Er3+掺杂无铅压电陶瓷0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT)，构筑了原子尺度的缺陷偶极子，通过缺陷偶极子与自发极化之间的耦合效应，提高了样品的退极化温度，阐明了缺陷偶极子与铁电畴跨尺度相互作用及协同效应。.4）提出多尺度极性结构与局域应力场协同调控与优化热释电材料性能新方法，设计制备了多种高质量0-3型半导体/反铁电复合陶瓷, 通过畴形态和相结构在温度、应力和电场等外物理场作用下的演变规律，揭示了复合陶瓷局域应力场与微结构之间的物理机理。.基于上述主要结果，发表包括Nature Communications、Advanced Functional Materials、Nano Energy、APL Materials、ACS Applied Materials & Interfaces、Journal of the American Ceramic Society、Advanced Materials Technologies和物理学报等论文24篇。申请中国发明专利20件，美国专利1件，授权中国发明专利3件。作国际学术会议邀请报告13次。