射频复合大功率铁氧体高频动态损耗机理研究

The project focuses on the preparation of the low-loss RF composite high-power ferrite and the study of its dynamic loss mechanism at high frequency. The study contents include: 1) Preparation of low-loss RF composite high-power ferrite materials; 2) The study on the relationship between the high-frequency dynamic loss and permeability spectra; 3)Research on the relationship between high-frequency dynamic loss and magnetic domain; 4) The determination of quantitative relationship of the high-frequency dynamic loss. Adopting an innovative technology in which the BST nanocrystalline is implanted to MnZn ferrite,which will form the perovskite-spinel phase composite structure, combined with the interaction of composite additives, the RF composite high-power ferrite materials are sintered at low temperature. According to the realationship that the permeability spectra changes with the frequency, the magnetic loss and energy storage, the domain-wall motion loss and domain rotation loss will be studied. The activity of the mechanism of the high-frequency dynamic loss will be cleared, and the potential energy of domain walls, elastic energy and kinetic energy as well as the relationship between loss and grain size will be studied. The Steinmetz coefficient and frequency index, and quantitative relationship of eddy current loss will be cleared through studying on the relationship of the high-frequency dynamic loss. This research project has great significance to solve four scientific issues which include the relationship between the high-frequency dynamic loss and the key preparation process, the dependence between the domain-wall movement loss and the domain rotaion loss, the relationship among the domain-wall potential energy, elastic energy and kinetic energy, and the determination of the quantitative relationship of the high-frequency dynamic loss.

本项目针对低损耗射频复合大功率铁氧体制备及其高频动态损耗机理展开研究。研究内容包括：1）低损耗射频复合大功率铁氧体材料制备；2）高频动态损耗与磁谱间关系研究；3）高频动态损耗与磁畴形态间作用关系研究；4）高频动态损耗定量关系式确定。创新性的利用BST纳米晶植入MnZn铁氧体技术，形成钙钛矿-尖晶石相双相复合结构，结合复合添加剂交互作用，低温烧结射频复合大功率铁氧体材料；基于磁导率随频率的变化关系，研究磁损耗和储能以及壁移损耗和畴转损耗；明确高频动态损耗作用机理，研究损耗与晶粒尺寸关系以及畴壁势能、弹性能及动能；研究高频动态损耗关系式，明确斯坦梅兹系数和频率指数、涡流损耗定量关系式等。项目研究对于解决射频复合大功率铁氧体材料高频动态损耗与关键制备工艺、壁移损耗与畴转损耗、畴壁势能、弹性能与动能间关系以及高频动态损耗定量关系式确定四个科学问题有重要意义。

功率电子学的快速发展对高频开关电源提出了更高的要求，使电源模块的工作频率逐渐向MHz频段推进。而制约开关电源实现高频化、小型轻量化、平面贴装化目标的主要瓶颈是应用于其中的射频复合大功率铁氧体材料，该类材料作为MHz级开关电源的核心，完成功率的转换与传输，是MHz级开关电源的基础性支撑材料。而作为目前世界上使用频率（2~4MHz）最高的射频复合大功率铁氧体材料，其制备技术及高频动态损耗机理的认识一直是国内外同行亟待解决的科学难题。本项目以尖晶石铁氧体材料为研究对象，对射频复合大功率铁氧体制备技术和高频动态损耗机理进行研究，以通过磁化阻力/磁化动力调控、磁畴形态与动态损耗间关联认识等措施，显著降低了材料的高频损耗。发表SCI论文11篇，申请专利3项，授权1项，培养博士生4名、硕士生11名。取得的代表性研究成果如下：（1）完成了超低损耗射频复合大功率铁氧体材料的制备。采用固相反应法制备了射频复合大功率铁氧体材料，完成了显微结构、磁性能及高频动态损耗与关键工艺参数间关系研究，明确了超低损耗射频复合大功率铁氧体材料的实现条件及规律认识，成功制备出当前世界上可查的最优高频低损耗铁氧体材料。（2）完成了磁畴形态与磁化机制间关系研究。通过洛伦兹电镜观察到射频复合大功率多晶铁氧体材料的磁畴形态，厘清了该材料的单畴临界尺寸，并深入探究了磁化机制与动态损耗作用关系。（3）完成了射频复合大功率铁氧体材料布里渊函数温度特性研究。提出了“等效自旋量子数”的思想，修正了次晶格具有多种磁性离子的射频复合大功率铁氧体材料的布里渊函数表达式，明确了分子场系数与居里温度间变化关系。（4）完成了射频复合大功率铁氧体材料高频动态损耗的调控及产生机理认识。基于磁化动力与阻力动态调控铁氧体材料磁导率的物理思想，构建了高电阻晶界层和均匀细小晶粒显微结构，实现了动态损耗的调控及产生机理认识，厘清了MHz频段动态损耗定量关系。