基于同步辐射的铋基钙钛矿无铅铁电陶瓷压电响应及其相结构本质研究

Recently, the lead-free ferroelectric materials and related physical mechanisms have been the hot and leading edge topics in condensed mater and material science fields. Bismuth-based perovskite ferroelectrics showing excellent ferroelectric and piezoelectric performance are one of the most promising lead-free piezoelectric materials. At present their performance are difficult to improve by simply doping and processing modification. Moreover, these materials have diverse and very complex phase structures, and the researchers have not reached a consensus on it. At the same time the effects of the phase transition and displacement of cations and oxygen on the piezoelectric response are still not clear. This difficulty has become the bottleneck for developing the high-performance bismuth-based perovskite lead-free ferroelectric materials. The proposed project are aiming to uncover the fine phase structures, local structure and phase structure related piezoelectric response of the bismuth perovskite lead-free ferroelectric materials by the third-generation synchrotron radiation in Shanghai Synchrotron Radiation Source. On the basis of the construction of bismuth-based compositions with various types of phase boundaries, the characteristics of the phase structures, local electronic structures, geometric structure properties and ion displacement at various temperatures, stress and electric fields as well as their effects on the dielectric, ferroelectric, piezoelectric and field-induced strain properties will be systematically explored to clarify the mechanisms of polarization rotation, lattice distortion and domain switching on the atomic scale in these materials. The project will also build up the universal diagrams of “temperature-composition-phase” and “electric field-compositions-phase” for the typical bismuth-based lead-free ferroelectric materials. It will be expected to establish solid theoretical and experimental bases for developing new generation lead-free ferroelectric and piezoelectric materials. This research will also help to enrich the present ferroelectric and piezoelectric theories.

无铅铁电材料及相关压电物理问题成为材料科学和凝聚态领域最为热门的前沿课题，铋基钙钛矿铁电体性能优异，是最有前途的无铅压电体系之一。但目前通过简单的掺杂改性和改进制备工艺，很难进一步提升其性能，其相结构丰富复杂，学界未达成共识，相变及原子位移对压电响应的影响机理尚不明确，成为制约铋基钙钛矿铁电材料发展的瓶颈。项目以揭示钙钛矿无铅铁电材料精细相结构和局域微结构对压电响应的影响机制为目的，构建不同相界类型的铋基铁电材料，利用上海光源第三代同步辐射技术，深入研究温度、电场和压力变化下相结构、局域电子结构和几何配置以及原子位移等变化规律，及其与介电、铁电、压电和电致应变等宏观特性的内在联系，从原子尺度解释铋基材料极化转向、晶格畸变和电畴翻转机理。建立典型铋基钙钛矿铁电材料“成分-温度-相结构”及“成分-电场-相结构”的普适相图，为设计新型高性能无铅铁电压电材料提供实验和理论依据，丰富铁电、压电理论。

铋基钙钛矿铁电体性能优异，是最有希望得到商业应用的无铅铁电压电体系之一。目前绝大多数研究关注的都是性能的提升方法，但是关于其优异性能的结构本质研究甚少。另外，铋基钙钛矿铁电体的精细结构、相变及原子偏移对介电、铁电、压电和应变响应的影响机理尚不明确，这使得铋基钙钛矿铁电材料的进一步发展遇到瓶颈。本项目首先利用掺杂、织构、复合等手段构建出了多种高压电、应变和铁电性能的铋基无铅铁电陶瓷体系，然后采用上海光源第三代同步辐射技术，在不同的温度、电场和压力变化下测试材料的相结构、局域电子和原子结构，掌握其变化规律，分析其与铁电、压电和电致应变等电性能的内在关系，最后在原子尺度解释铋基无铅铁电材料的极化行为机制、晶格畸变本质和电畴翻转的机理。本项目从根本上建立起典型铋基钙钛矿铁电材料的“成分-微结构-电场（温度场）-性能”之间的规律模型，揭示了钙钛矿无铅铁电材料精细相结构和局域微结构对压电应变响应的作用机制，为无铅铁电陶瓷材料的研究提供了新视角和新方法。并且，为后续设计高性能无铅铁电压电材料提供理论指导和实验支撑，丰富了铁电、压电相关物理理论，具有重要的理论和现实意义。