钙钛矿结构铁电陶瓷纳米畴的关联有序性、极性与活性及弱场压电性能的来源

The origin of piezoelectricity of the perovskite structure ferroelectric ceramics is one of the core issues in piezoelectric materials study field for understanding and solving the inferior properties of lead-free piezoelectric materials. By discriminating weak field piezoelctric response from high filed-induced-stain, and basing on weak field piezoelctric properties origirating from two core processes of poling electric field constructing nanodomains ordering and their piezoelctric responses under weak field, the viewpoint that piezoelectric properties come from the correlation ordering, polarizability and activity of nanodomians and their weak field piezoelectric responses has been proposed. Representative morphotropic phase boundary composition of Pb-free of Bi1/2Na1/2TiO3-BaTiO3(BNT-BT), Ba(Zr0.2Ti0.8)O3- (Ba0.7Ca0.3)TiO3(BZT-BCT) and Pb-based of Pb(Zr, Ti)O3(PZT) ferroelectric ceramics will be selected as representative material systems. The effect of composition, doping and preparation process on size, density, polarizability and activity of nanodomain will be investigated. The percolation behavior of nanodomains and their constructing process of correlation ordering under electric fields will be studied. The correlation between nanodomains correlation ordering and external field, phase, crystal structure, domain size, domain structure will be explored. Model of piezoelectric responses of ordering nanodomains will be established by thermodynamics phenomenological theory. The intrinsic correlation between weak field piezoelectric responses and correlation ordering, size, polarizability and activity of nanodomain and composition(whether contains lead) will be researched. Based on above results, the key scientific problems including the relation between high piezoelectric activity of Pb-based materials and lead element, internal origin of weak field piezoelectric activity in perovskite structure ferroelectric ceramics, will be clarified. The results will make a theoretical and experimental foundation for the study and development of high-performance lead-free piezoelectric materials.

钙钛矿结构铁电陶瓷的压电活性来源问题是理解无铅压电材料性能不足及解决压电材料无铅化最核心的问题之一。本项目通过区分高场/弱场两种不同类型的压电机理，基于弱场压电性能来源于极化建立有序纳米畴以及弱场下有序畴的压电响应这两个关键过程，提出弱场压电性能来源于纳米畴的关联有序性、极性与活性及弱场下的压电响应。项目以准同型相界组成的无铅陶瓷钛酸铋钠-钛酸钡与锆钛酸钡钙以及铅基陶瓷锆钛酸铅为代表体系，研究组成、掺杂、工艺对纳米畴尺寸、密度、极性及活性的影响；探索纳米畴在电场作用下的渗流行为及关联有序建立过程；通过热力学唯象理论建立有序纳米畴的压电响应模型，研究纳米畴关联有序性、极性、活性以及畴组成(是否含铅)与弱场压电响应的内在关联，阐明压电活性与铅的关系，以及弱场压电性能的来源等关键科学问题，研究结果为研究与开发高性能无铅压电材料奠定理论与实验基础。

压电陶瓷及相关器件广泛应用于换能器、微位移器、传感器、谐振器及滤波器等领域，是一种不可或缺的高技术新材料之一，目前广泛研究的无铅压电陶瓷材料综合性能远远低于铅基材料。因此，探索钙钛矿结构铁电陶瓷压电活性的来源问题是理解无铅压电材料性能不足及解决压电材料无铅化最基础、最核心的问题之一。项目在BNT-xBT与BZT-xBCT无铅体系中，通过成分设计、掺杂以及气氛烧结调控纳米畴的尺寸、密度、极性以及活性。通过外场激发建立纳米畴的关联有序。借鉴极性纳米微区的在电场下渗流有序行为，采用渗流理论/模型研究纳米畴的渗流有序行为及关联有序建立过程，研究纳米畴关联有序性、极性与活性以及纳米畴结构与组成对弱场压电响应的影响，揭示了弱场压电响应的来源问题。项目利用纳米畴亚稳特性及在外场有序排列行为，通过纳米畴结构及外场反转特性，在BNT基陶瓷中实现了d33=1658 pC/N，电致伸缩系数Q = 0.287m4C-2，高场巨应变S=0.6%，巨压电应变系数 =17816pm/V。在BT体系中实现d33=1634pC/N，偏场压电应变常数 =2032 pm/V，介电常数εr~105，介电可调度~98%等优异性能。项目结果将为压电材料的结构和性能优化、新型无铅压电材料的设计与实际应用提供参考与依据，将拓宽和加深压电效应的来源理论内涵的认识。研究结果受到国内外同行认可，目前发表20篇SCI收录论文，10件授权发明专利。

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