A competitive reaction strategy toward dielectric phases for enhancing electromagnetic wave absorption of polymer-derived ceramics

Abstract

SiBCN ceramics have a wide range of applications in the field of high temperature electromagnetic wave (EMW) absorption owing to their excellent EMW attenuation and oxidation resistance. However, excessive SiC and insufficient Si₃N₄ in the SiBCN ceramics deteriorate the impedance matching characteristics, and weaken the absorption ability for EMW. In this paper, the amount of SiC and Si₃N₄ is balanced by a competitive reaction strategy, in which HfZr atoms are introduced to modulate the dielectric phases in the SiBCN ceramics. The formation of a HfZrCN compound produces a cage-like structure around Si₃N₄, inhibiting the reaction of Si₃N₄ with carbon to form SiC. The appropriate amounts of SiC and Si₃N₄, and the abundant interfaces and defects jointly enhance the EMW absorption capability by simultaneously improving the impedance matching and attenuation capability. Thus, an effective absorption band of 4.96 GHz (11.20–16.16 GHz) is reached with a thickness of 1.7 mm for the HfZr-SiBCN ceramics. This work provides a new strategy for simultaneously improving the impedance matching and EMW attenuation capability of polymer-derived ceramics by introducing difficult-to-migrate atoms to regulate the content of the dielectric phase.