Graphene/silicon nitride (GR/Si₃N₄) ceramic composites with uniformly dispersed GR sheets were prepared using spark plasma sintering. The effects of GR content on the microstructure and electrical properties of the composites were investigated in detail. With the GR content rising, the conductive GR network was formed in the composites, leading to the appearance of a percolation phenomenon, and the conductive mechanism also changed from hopping conductivity to metal-like conductivity. When the GR content reached the percolation threshold, the composites showed a negative permittivity behavior, which resulted from the low frequency plasmonic state generated by the formative conducting GR networks. The increasing GR content resulted in a higher plasma frequency and larger magnitude of negative permittivity, which was consistent with the analysis of Drude model. A relatively high dielectric loss was observed in the composites and mainly induced by the high leakage current among GR sheets. Our work is beneficial to expound the regulation mechanism of negative permittivity, and the obtained ceramic composites present some potential applications in microwave absorption, shielding and capacitors.

中文翻译：

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火花等离子体烧结制备石墨烯/氮化硅复合材料的射频负介电常数

石墨烯/氮化硅（GR / Si ₃ N ₄使用火花等离子体烧结制备具有均匀分散的GR片的陶瓷复合材料。详细研究了GR含量对复合材料微观结构和电性能的影响。随着GR含量的增加，复合材料中形成导电GR网络，导致出现渗流现象，其导电机理也从跳跃导电性转变为类金属导电性。当GR含量达到渗滤阈值时，复合材料显示出负介电常数行为，这是由形成性导电GR网络产生的低频等离子体状态引起的。GR含量的增加导致更高的等离子体频率和更大的负介电常数，这与Drude模型的分析是一致的。在复合材料中观察到相对较高的介电损耗，这主要是由GR片之间的高泄漏电流引起的。我们的工作有益于阐明负介电常数的调节机理，并且所得的陶瓷复合材料在微波吸收，屏蔽和电容器中具有一些潜在的应用。