X-site nitrogen engineering of V 2 GaC MAX phase for enhanced microwave absorption

Abstract The increasing proliferation of 5G/6G communication systems and artificial intelligence technologies has intensified electromagnetic pollution, creating an urgent demand for lightweight, efficient, and thermally stable electromagnetic wave (EMW) absorbers. MAX phases have emerged as promising candidates owing to their unique layered structures and excellent electrical conductivity; however, performance optimization has largely focused on M- and A-site engineering, while X-site regulation remains largely unexplored. Herein, a series of X-site nitrogen-substituted MAX phases, V2GaC1-xNx (x = 0.25, 0.5, 0.75, and 1), were successfully synthesized and their EMW absorption behaviors systematically investigated. Benefiting from nitrogen-induced modulation of the electronic structure and dielectric response, V2GaC0.75N0.25 achieved an exceptional minimum reflection loss (RLmin) of −71.87 dB at an ultrathin thickness of 1.26 mm, while V2GaC0.25N0.75 exhibited a maximum effective absorption bandwidth (EAB) of 5.2 GHz. Furthermore, efficient EMW attenuation covering the entire 2–18 GHz frequency range was achieved through thickness modulation. Notably, pro-oxidized V2GaN still maintains excellent microwave absorption performance when measured at room temperature after oxidation treatment at 500 ℃, exhibiting an RLmin of −60.89 dB and an EAB of 3.59 GHz, demonstrating excellent thermal stability of its electromagnetic response. This work demonstrates that X-site nitrogen engineering can effectively regulate the electromagnetic response of V2GaC MAX phase, providing an compositional strategy for the design of high-performance V2GaC microwave absorbers while offering valuable theoretical insights for X-site engineering in other MAX-phase systems.