碱金属铌酸盐基无铅铁电陶瓷的相界特性和高压电活性相关性的同步辐射研究

The relation issue between the structure and property of ferroelectric and piezoelectric materials belongs to a fundamental science, characteristic of the universality and practicability. To clarify the change of the phase structure and local micro-structure of the material under various conditions and its effect on the material properties is taken as a research idea. To enrich and improve the fundamental theory of ferroelectric and piezoelectric ceramics, and to disclose the inherent correlation between the phase coexistence and high piezoelectric performances are taken as a research goal. The advanced experimental platform of the third-generation synchrotron radiation in Shanghai Synchrotron Radiation Source will be employed in this project. We attempt to deal with the relationship between the composition-phase structure-local electronic and geometric structure-property of the alkaline niobate which has been taken as a typical lead-free candidate. On the basis of the construction of niobate-based compositions with different types of phase boundaries such as rhombohedral-orthorhombic, orthorhombic-tetragonal and rhombohedral-tetragonal boundaries, the fine phase structure and local micro-structure of niobate-based lead-free piezoelectric materials close to the phase boundary, and the characteristics of their responses to various fields such as temperature, stress and electric field will be systematically explored for the purpose to clarify the modulation law and mechanisms of the phase transition and to build up a universal diagram of the polarization switching in different phases under an electric field. The structural foundation of phase coexisted niobate based ceramics with high piezoelectric activity will be theoretically disclosed. It will be expected to establish a solid theoretical base for driving the industrial application of alkaline niobates of such a promising lead-free material.

针对铁电压电材料结构与性能关系问题的普遍性、实用性和基础科学性，以阐明材料的相结构和局域微结构在各种外在条件下的变化及其对材料性能的影响为研究思路，丰富与完善铁电压电陶瓷材料的基础理论和揭示相共存和高压电性能的内在联系为研究目的，本项目利用上海光源第三代同步辐射的先进实验技术平台，紧紧围绕碱金属铌酸盐这一典型的无铅体系的组成-相结构-局域电子和几何结构-性能的关系，构建具有不同相界类型（菱方-正交、正交-四方和菱方-四方）的铌酸盐组成，系统探索铌酸盐基无铅压电材料在相界附近的精细相结构和局域微结构，以及它们对各种外场（温度、压力、电场）的响应特征，阐明其相变的调制规律和作用机理，建立铌酸盐体系中不同相结构在电场作用下极化翻转的普适谱图，进而从理论上揭示不同相界组成的铌酸盐基陶瓷具有高压电活性的结构根源，为推动碱金属铌酸盐这一颇具应用潜力的无铅压电材料的产业化应用奠定坚实的理论基础。

本基金项目分别以NKN和NN为基的两种典型碱金属铌酸盐无铅铁电压电陶瓷为研究对象，借助高分辨同步辐射等技术手段研究了组成-相结构-局域电子和几何结构之间的关系，系统探索了铌酸盐基无铅陶瓷在不同相界附近的精细相结构及其对温度、电场等外场作用下的响应特征，阐明了高压电活性，场致应变特性及其温度依赖性等基础问题的作用机理，建立起碱金属铌酸盐在电场作用下极化翻转的普适图谱，成功开发出无铅无钾、具有R和T共存且具有准同型相界特征的无铅压电陶瓷，并阐明其具有优异热稳定的压电和机电性能的结构基础，为推动铌酸盐基无铅压电陶瓷产业化应用奠定了很好的实验和理论基础。

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