金属陶瓷的射频负介电行为调控及机制研究

Ever-increasing attention has been paid to double negative materials due to their fascinating potential applications in electromagnetic cloaking, telecommunications and data storage, etc. At the present time, arrays of periodic unit cells are usually needed for the realization of double negative property. In our recent work, radio frequency double negative property is realized in novel metal/ferrite composites consisting of metallic phase randomly dispersed in ferrite matrix. In the composites, negative permittivity is provided by metal, and negative permeability is provided by ferrite. This program will focus on the adjustment and mechanism of the radio frequency negative permittivity in metal/ferrite composites. The main research contents are as follows: for the adjustment of negative permittivity, experimental research and theoretical calculation will be carried out to clarify the influence of the species, morphology, volume fraction and distribution of metallic phase on the negative permittivity behavior; for the negative permittivity mechanism, the interrelationship between the electron transportation behavior, reactance characteristic and frequency dispersion of negative permittivity will be established using percolation theory, electron transportation theory and equivalent circuit theory, etc. The present project will clarify the influence of composition and microstructure of cermets on their radio frequency negative permittivity behaviors. And it will be very helpful for the preparation of double negative materials with tunable dielectric property. Besides, the reveal of radio frequency negative permittivity mechanism has important significance for the enrichment and improvement of double negative theory.

双负材料在电磁隐身、通讯和信息存储等领域具有重要应用前景，是国内外研究的热点。目前，双负性质通常需要构造周期性结构单元阵列来实现。申请者近期研究发现，在铁氧体陶瓷中添加呈随机分布的金属相，其中：金属提供负介电，铁氧体提供负磁导率，可以制备一种新型的不含有周期性结构单元的射频金属/铁氧体双负材料。本项目着眼于这类新型双负材料的介电性能调控和负介电机理，拟开展以下研究：针对负介电调控，结合实验探索和理论计算，探明金属相种类、形貌、体积分数和分布等对负介电的影响规律；针对负介电机理，综合运用逾渗理论、电子输运理论和等效电路理论等建立电子输运行为、电抗特性和负介电频散特性之间的联系，进而揭示射频负介电机理。经本项目研究，阐明金属陶瓷成分和微结构对负介电的调控规律和机制，对制备介电性能可调控的双负材料具有重要的借鉴意义；揭示金属陶瓷射频负介电机理，对丰富和完善双负材料理论体系具有重要意义。

电磁双负材料在电磁隐身、通讯和信息存储等领域具有重要应用前景，本项目着眼于双负材料的负介电性能调控和机理，主要研究内容包括：针对负介电调控，探索金属相种类、形貌、体积分数及分布等对负介电的影响规律；针对负介电机理，综合运用逾渗理论、电子输运理论和等效电路理论等建立电子输运行为、电抗特性和负介电频散特性之间的联系。本项目通过调整铜/钇铁石榴石复合材料中铜的含量实现了负介电常数在10MHz至1GHz频段内的有效调控，并探讨了法诺共振型介电频散机理。此外，在银/氧化铝金属陶瓷中发现了基于带间电子转移共振的负介电频散现象并探讨了其机理。为了进一步拓展负介电材料的应用领域，本项目创新性地将正介电材料和负介电材料结合到一起，设计出一种新型的正/负介电叠层高介电复合材料。研究表明，该双层复合介质的介电常数可达400 @10 kHz，远高于单层材料(~20 @10 kHz)。同时，损耗因子仅为0.06 @10kHz，与正介电层的损耗因子相当（~0.05 @10 kHz）。为了解决双层复合材料介电击穿强度较低的问题，通过构造三层结构正负介电叠层复合材料获得了显著高于双层材料的击穿强度，大大促进了其在电力电容器、天线介质基板以及电容触控屏等电力电子器件中的应用。总之，本项目关于负介电金属陶瓷性能调控规律及机制的研究将为电磁双负材料的设计、制备和性能调控提供丰富的借鉴，有效地推动电磁双负材料在电磁隐身、微波衰减、天线及电子电力系统中的应用。