钙钛矿陶瓷基全介质型超表面黑体及可调性研究

Metasurface blackbody can almost absorb all of the electromagnetic waves radiating onto it. In addition, the two-dimensional structure itself has the advantages of light weight, thin thickness, and small size, thus the metasurface absorbing material shows great application prospects. Impedance matching and critical loss are necessary conditions for constructing metasurface blackbody based on the principle of resonant absorption. Therefore, in order to achieve the matching of material equivalent impedance and free space impedance, no transmission, and total absorption effect, currently reported metasurface blackbodies are mostly the metal-medium hybrid resonant cell structures arranged on a metal substrate. Due to low melting point and high frequency loss, metal-based metasurface blackbodies may be limited in the application. Ceramic materials possess the high melting point and low ohmic losses. They are of great significance to realize all-dielectric metasurface blackbodies. Perovskite ceramic materials have higher dielectric constants and moderate dielectric losses, and the microwave metasurface blackbodies not having metal structures can be achieved by the resonant absorption of perovskite ceramic particles. This project uses perovskite ceramic materials to prepare dielectric resonator particles and assemble them into a two-dimensional surface with a certain period, thus it can completely absorb the electromagnetic energy radiated from outside. Moreover, the resonant frequency of the dielectric particles varies with temperature, and thus a thermally tunable metasurface blackbody is realized and the application range is expanded.

超表面黑体(Metasurface Blackbody)几乎可以完全吸收照射到其上的电磁辐射，加之二维结构本身具有质量轻、厚度薄、体积小等优点，这种吸波材料显现出巨大应用前景。阻抗匹配和临界损耗是这种基于谐振吸收原理构筑超黑表面的必要条件。所以，为实现材料等效阻抗与自由空间阻抗匹配及无透射全吸收效果，目前报道的超黑表面大多是金属基板上排列的金属-介质混合谐振单元结构。由于金属的熔点低、高频损耗大，金属基超表面黑体的应用会受到限制。.陶瓷材料的熔点高、欧姆损耗小，探索实现陶瓷基全介质型超表面黑体具有重要意义。钙钛矿陶瓷材料具有较高介电常数和适中介质损耗，利用钙钛矿陶瓷颗粒的谐振吸收可实现微波超黑表面的去金属化。本项目利用钙钛矿陶瓷材料制备介质谐振颗粒，按照一定周期组装成二维结构，使之完全吸收外界辐射的电磁能量。而且，介质颗粒的谐振频率随温度变化，由此可实现热可调超黑表面，大大扩展其应用范围。

本项目主要涉及钙钛矿陶瓷基全介质型超表面黑体的研究，以钙钛矿陶瓷为原料，制备具有一定介电常数和损耗的亚波长介质谐振器，作为超表面黑体的基本单元结构。研究介电常数和几何结构参数对介质谐振器形成的电偶极子谐振和磁偶极子谐振的影响规律、介质损耗对构建的二维超表面的反射、透射和吸收的影响规律。结果表明，对于较高介电常数的钙钛矿陶瓷颗粒谐振器而言，其产生的电偶极子谐振和磁偶极子谐振符合亚波长尺度的要求，能够作为超表面黑体的基本单元。调节介质谐振器几何结构参数，使电偶极子和磁偶极子在同一频率点谐振，此频率点处的超表面结构等效介电常数和磁导率的实部就会相等。调节材料损耗使其达到一个临界值，就会使超表面结构等效介电常数和磁导率的虚部相等且能达到一个极大值，从而与外界空气阻抗完全匹配，实现了黑体完全吸收外界入射电磁能量的基本要求。以氧化铝和氧化铍的复合结构为基本单元，构建了半径为6毫米、厚度为7毫米的二维超表面结构，测试结果表明此超表面结构能够吸收大于90%的入射电磁能量，达到了近似黑体吸收的要求。本项目提出的全介质型超表面黑体具有吸收强、质量轻、厚度薄、频率可调等优点，在辐射热仪、传感器、电磁波隐身等方面具有潜在的应用价值。若选用热电或其他陶瓷，还能实现受外场调控的超表面黑体，促进其向智能化的方向发展。