Nickel/yttrium iron garnet metacomposites with adjustable negative permittivity behavior toward electromagnetic shielding application

Abstract

Recent advancement of metacomposites with negative permittivity has provided a new research approach for the design and construction of electromagnetic (EM) shielding materials. Here, we fabricated nickel/yttrium iron garnet (Ni/YIG) metacomposites by a convenient liquid impregnation approach and explored their electromagnetic properties at MHz and Ku bands. As the Ni content increased, some isolated Ni particles formed three-dimensional interconnected networks in the composites, leading to the changes of conducting mechanism and reactance characteristic. A negative permittivity behavior was observed in the composites with high Ni contents, which was put down to low-frequency plasma state of free electrons in the completed Ni networks. The dispersion of negative permittivity at frequencies below 10 MHz was affected by the isolated metal particles and could be well described by the Drude-Lorentz model. An impressive shielding effectiveness of 33.1 dB was achieved at Ku band with a reflection-dominated mechanism, which was ascribed to the negative permittivity induced impedance mismatch. The inductive conducting networks were vital building blocks in the metacomposites for realizing negative permittivity and improving EM shielding performance. This work offered guidance for designing EM shielding metacomposites and promoted the next development of this field.