Enhanced electromagnetic wave absorption properties of ZIF‐67 modified polymer‐derived SiCN ceramics by in situ construction of multiple heterointerfaces

Abstract Multiphase polymer‐derived ceramics have the advantages of thermal stability and adjustable dielectric properties, which exhibit significant potential for use in high‐temperature microwave absorbing materials. Herein, Co‐containing polymer‐derived SiCN (Co–SiCN) ceramics were successfully synthesized by the physical mixing of zeolitic imidazolate framework (ZIF)‐67 and polysilazane precursors and subsequent pyrolysis. The phase and chemical compositions, microstructures, dielectric properties, electromagnetic wave absorption (EWA) performance, and mechanism of the ceramics were investigated. The results showed that the introduction of ZIF‐67 promoted the in situ formation of dielectric loss phases, including SiC nanocrystals, CoSi nanocrystals, and free carbon. The phase composition can be regulated by controlling the pyrolysis temperature to achieve ideal EWA properties. The Co–SiCN ceramic pyrolyzed at 1500 °C demonstrated excellent EWA performance, with a maximum effective absorption band (EAB max ) of 3.0 GHz at an ultralow thickness of 1.05 mm and minimum reflection loss (RL min ) of − 46.4 dB at a low frequency of 6 GHz. Compared with other reported SiCN‐based ceramics containing magnetic metals, the ceramics prepared in this study stand out because of their low RL and high EAB at low thicknesses. The superior microwave absorption performance of the Co–SiCN ceramics is attributed to the heterointerface polarization, and impedance matching induced by the synergistic effects of their co‐existing electromagnetic transparent/absorption phases. This study provides new insights into the development of high‐performance SiCN‐based microwave absorbers.