Joule heating‐driven ultrafast synthesis of high‐entropy MAX phase as a robust electromagnetic wave absorber

MAX phases can benefit from high‐entropy (HE) effects to enhance their electromagnetic (EM) wave absorption properties. This study introduces Joule heating‐driven ultrafast synthesis (JHUS) for the first time to synthesize the novel HE‐MAX phase (Ti 1/5 Nb 1/5 Ta 1/5 Hf 1/5 V 1/5 ) 2 AlC at 1200°C in 20 s. The high‐entropy effects, combined with the JHUS, lead to the formation of structural defects within the HE‐MAX phase, such as lattice distortions, dislocations, and point defects. These structural defects play a crucial role in promoting dipole polarization. The high aspect ratio of the layered structure promotes electron transfer and interfacial polarization. These effects result in a significant improvement in EM wave absorption, with a minimum reflection loss of −46.07 dB at 2.7 mm and a 4.08 GHz absorption bandwidth at 1.5 mm. This study demonstrates an efficient and rapid method for synthesizing HE‐MAX phases and explores the role of high‐entropy engineering in optimizing their EM wave absorption.