无铅压电纳米线的性能调控及其微纳能量收集元件的构建研究

The research and development of high-performance micro-scale energy harvesting devices will be of great importance in the integration of micro-devices. Due to the relatively low piezoelectric constant of lead-free piezoelectric materials as well as the low open-circuit voltage of the energy harvesting micro-devices, this proposal aims to realizethe orientation growth of K1-xNaxNbO3 (KNN) lead-free piezoelectric nanowires through the supercritical hydrothermal process. The as-synthesized nanowires will be annealed under oxidizing or reducing atmospheres. The effects of defect type, concentration and distribution in the nanowires on the carrier transportation, polarization and piezoelectric properties will be studied under the assistance of slow positron annihilation spectroscopy. The physical mechanism of the defect-related property-modification in the nanowires will be revealed. Based on that, the stress field distribution inside the nanogenerators will be studied by using the finite element analysis method. The influence of the assemly type of the nanowires on the piezoelectric potential will also be investigated.The relationship between the device architecture and the energy harvesting and conversion efficiency of the nanogenerators will be studied. Then the assembly of KNN nanowires on the flexible substrates will be investigated to obtain the micor-scaled piezoelectric energy harvesting devices which can harvest and convert the abundant mechanical energy around the environment into output electrical energy, as well as the self-powered gas sensor systems. The smooth implementation of this project will provide the theoretical and experimental basis for the property optimization of lead-free piezoelectric nanowires and the developmentof micro/nano-scaled piezoelectric energy harvesting devices, and promote the development and practical application of micro/nano-devices.

高性能微纳能量收集器的研制对促进微纳器件的集成化发展具有重要意义。针对无铅压电纳米线压电常数不高和微纳能量收集器的开路电压不理想等问题，本项目提出采用超临界水热合成技术实现K0.5Na0.5NbO3(KNN)压电纳米线的取向生长，在氧化或还原气氛中对纳米线进行退火处理，结合慢正电子湮灭谱技术研究纳米线中的缺陷种类、浓度和分布等对电输运、极化和压电性能的影响，探明缺陷调控纳米线压电性能的物理机制。在此基础上，采用计算机仿真研究纳米发电机在外力作用下的应力场分布，分析纳米线组装方式对压电势的影响，探索器件构型与能量采集和转化效率的关联性。研究KNN纳米线在柔性衬底上的组装技术，研制出能够采集并转化环境中富余机械能的高性能微纳压电能量收集器和自驱动气体传感器。本项目的顺利实施，将为无铅压电纳米线的性能优化和微纳压电能量收集器件的发展提供理论依据和实验基础，对促进微纳器件的发展与应用具有重要意义。

高性能无铅压电纳米材料及其微纳能量收集器的研制对促进微纳器件的集成化发展具有重要意义。本项目围绕无铅压电(K,Na)NbO3(KNN)一维纳米材料，开展KNN纳米棒阵列等材料的可控生长、性能优化及其能量收集器件的系统研究。首先，通过衬底诱导的水热合成技术，在[100]取向的单晶SrTiO3衬底上实现了[110]取向正交相KNN单晶压电纳米棒阵列的取向生长，所得纳米棒沿轴向的压电性能优于其径向压电性能，与其[110]取向自发极化方向相符。通过在氧气气氛中对纳米棒进行退火处理，可实现纳米棒的组分、物相调控和表面氧空位钝化，从而将其轴向压电常数从140提高至360 pm/V。其次，利用多物理场有限元仿真设计能量收集器件，分析了KNN纳米线的长度及器件构型等因素对器件内产生的压电势的影响。结合微加工技术组装出多种能够采集并转化环境中富余机械能的高性能微纳压电能量收集器。在此基础上，将KNN等压电纳米线与微流控芯片相结合，还实现了对液体、气体等微流体能量的高效收集，构建了自供电微流控器件。此外，基于KNN纳米棒阵列的高效能量收集特性，还可实现了自供电的紫外传感。上述研究成果可为无铅压电纳米材料的性能优化和微纳压电能量收集器件的发展提供理论依据和实验基础，对促进自供电器件与系统的发展与应用具有重要意义。