Out-of-plane ordered quaternary (Cr_0.5V_0.5)₄AlC₃ MAX phase for high temperature stable electromagnetic wave absorption performance

MAX phases represent a large family of nanolaminated hexagonal compounds that have gained significant attention as potential candidates for high-temperature electromagnetic wave absorbers, attributed to their remarkable oxidation resistance and electrical conductivity. However, the dielectric and absorbing performance of out-of-plane ordered 413 MAX phase remains unexplored. In this study, we have synthesized the quaternary MAX phase (Cr_0.5V_0.5)₄AlC₃ via solid-state reaction between Cr₂AlC and VC, achieving a purity of up to 90.1 wt%. The out-of-plane ordering of (Cr_0.5V_0.5)₄AlC₃ is confirmed for the first-time using STEM-EDS analysis. The oxidation behavior of (Cr_0.5V_0.5)₄AlC₃ is investigated, revealing an oxidation onset temperature of 756 °C, indicative of good oxidation stability. Additionally, the microwave absorption properties are evaluated through dielectric parameter and reflection loss measurements. (Cr_0.5V_0.5)₄AlC₃ powders exhibited exceptional electromagnetic wave absorption, with a sample of 2.6 mm thickness achieving a minimum reflection loss of −47.6 dB and an effective absorption bandwidth of 6.3 GHz, the widest among all reported pure MAX phases. Even after oxidation at 600 °C for 1 h, the sample maintained an absorption bandwidth of 5.2 GHz. This study provides valuable insights into the preparation and application of out-of-plane ordered MAX phases for electromagnetic wave absorption at operating temperatures.