稀土掺杂铁酸铋材料弛豫中心构筑及变温微波吸收性能调控研究

Lightweight, high-efficiency and broadband microwave absorption material is the objective pursued in the modern military science, and is the important developing direction in civilian fields. Moreover, smart microwave absorption is the difficulty and hot subject of microwave absorption material, which has important scientific significance and application value for the precise electromagnetic protection and smart stealth. In this project, rare earth doped bismuth ferrite will be the materials. We aim at exploring the synthetic methods and cutting strategy of crystal structure. The multiple relaxation centre will be constructed on account of rare earth doping to control the structure of materials. The temperature and frequency dependences of electromagnetic properties of the materials will be investigated, and the correlation between the electromagnetic properties and the evolution of structure and electron structure will be analyzed. The nature effect of the relaxation centre on electromagnetic properties will be illuminated, and the variable temperature electromagnetic response mechanisms and microwave attenuation mechanisms will be demonstrated. It will help to realize the tuning of electromagnetic properties and microwave absorption, and obtain the tuning methods of selective frequency absorption driven by temperature. This study will provide new academic points and scientific ideas for smart microwave absorption materials design and tuning of properties, and will promote the development of electromagnetic protection and stealth technology.

轻质、高效、宽频吸波材料是现代军事科学长期追求的目标，也是民用科技的重要发展方向之一，更重要的是智能吸收是当代微波吸收材料的难点和热点课题，对于精确电磁防护及智能化隐身技术具有重要的科学意义与应用价值。本项目以稀土掺杂铁酸铋为研究对象，旨在探索稀土掺杂铁酸铋制备及其晶体结构剪裁方法，通过控制稀土元素掺杂调控铁酸铋微结构，构筑人工多重弛豫中心。研究材料微波电磁特性及温频特性，调查结构和电子结构与电磁性能的关联效应，阐明弛豫中心对电磁性能的作用本质，揭示变温电磁响应机制与能量衰减机制，有效调控变温电磁特性和微波吸收性能，建立基于温度驱动的频率选择吸收调控策略，为智能微波吸收材料设计及其性能调控提供新思路，促进电磁防护及隐身科学技术进步。

微波衰减材料一直以来是国防工程、信息安全及电磁辐射防护等技术领域的关键性材料体系。面对传统微波衰减材料吸收强度低、带宽窄及高温衰减性能差等缺点，开发新型高性能微波衰减材料已成为材料科学领域迫切完成的重要任务。本项目以同时具有介电、磁性能的铁酸铋材料为研究对象，以稀土La、Nd掺杂作为控制材料微观结构的手段，实现了弛豫中心的调控，从而达到了有效改善铁酸铋材料高温电磁参数及微波衰减性能的目的。研究发现，稀土掺杂实现了晶体结构、电畴、缺陷、极性界面等极性结构的调控，从而引起了本征极化、缺陷极化、界面极化及磁共振等对电磁波的响应，在不同频段产生了多种微波介电及磁弛豫。且随着温度的升高，稀土掺杂铁酸铋的介电弛豫具有明显的低频移动行为，基于第一性原理计算可知，这与其材料的晶格热振动具有密切的关系。更为重要的是，稀土掺杂的铁酸铋材料具有良好的微波衰减性能，其中La掺杂铁酸铋在吸收层厚度为2 mm时，最强反射损耗可达-54 dB，有效吸收带宽覆盖3.3 GHz，在吸收层厚度为1.8 mm时，有效吸收带宽覆盖整个X波段。Nd掺杂铁酸铋反射损耗超过了-20 dB，300 K到673 K之间吸收峰位移了2.8 GHz，实现了基于温度驱动的吸收频率的调控。本研究的开展为新型微波衰减材料提供了新的学术思想，为衰减性能调控发展了新的策略，实现了微波材料与隐身技术的创新。