力电共同作用下一维铁电纳米纤维的畴变机制

With the development of nano device, one-dimensional ferroelectric materials are widely used in ferroelectric random access memory. And the study of domain states is one of the basic way to understand the macroscopic properties. however, material size dramatically reduce makes no matter the characterization of electric domain in experiment, or domain switching mechanism in theory, have had a lot of challenges.In this proposal, we repectively observed the domain evaluation under the different mechanical stress and the polarizing voltage and mechanical stress simultaneously.On the other hand, Combining the nonlinear thermodynamic theory with surface bond contraction, the Gibbs free energy is constructed including surface layer, external stress and electric field and the other variables. According to this model, the different phase diagrams, the polarization-electric field hysteresis loops and the displacement-electric field curves can be obtained to research the phase transition and ferroelectric or piezoelectric properties. We aim to study the phase transition process under different mechanical stress or electric-stress coupling and present a reasonable domain switching mechanism for one-dimensional nanostructure.

随着器件纳米化的发展，一维铁电材料被广泛应用于铁电随机存储器。而对材料内部电畴的研究是深入了解其宏观性质的基本途径之一。然而，材料尺寸急剧的减小使得无论从实验上表征电畴的变化，还是理论上研究畴变的机理，都遇到了很大的挑战。本项目拟采用垂直和侧向压电力技术，分别观测外加力、电场作用下铁电纳米纤维的多场耦合畴变现象；采用非线性热力学理论并考虑纤维表面的键收缩效应，建立不同表面层数、外加应力、外加电场等包含多变量的自由能表达式，并得到外加应力、电场等不同变量下的关系相图及电滞回线、压电系数等性能的变化曲线。本项目旨在通过理论和实验相结合，研究铁电纳米纤维在外加力、电场作用下的相变过程和铁电、压电性能的变化规律，提出多场共同作用下一维纳米结构的畴变物理机制。

随着器件纳米化的发展，一维铁电材料被广泛应用于铁电随机存储器。而对材料内部电畴的研究是深入了解其宏观性质的基本途径之一。本项目以低维无铅铁电薄膜和铁电纳米纤维为研究对象，开展了制备技术和性能表征系统基础研究，探索材料在不同外场下畴变演化的实验观测方法并给出畴变的机理解释。重点研究两个关键科学问题：提出分析模型和表征方法准确表征外场下一维铁电纳米结构的畴变演化; 考虑表面层的键收缩效应和不同外场下的自由能表达式的建立。本项目得到了尺寸在100nm的超细BaTiO3纳米纤维。首次实现了不同力载荷下纳米纤维的压电力显微镜畴变观测。建立了外加力场下，外延生长在立方基底上单晶多畴铁电薄膜的热力学模型。发表SCI收录论文6篇，中文核心期刊1篇，培养硕士研究生5人。研究为铁电微器件在不同服役环境中的性能改变，提供了有用的数据参考。