High-temperature microwave absorbing properties of plasma sprayed La_0.5Sr_0.5FeO₃-Al₂O₃ coating

The application of high-temperature microwave-absorbing coatings (HTMACs) in the hot section of stealth aircraft engines holds substantial engineering significance. Refractory oxides serve as essential functional materials in HTMACs applications, primarily because of their modifiable electrical conductivity, superior chemical resistance, and ultra-high melting points. In this work, a La_0.5Sr_0.5FeO₃-Al₂O₃ pseudo-binary composite coating is successfully fabricated through a combined process of granulation and atmospheric plasma spraying. This investigation systematically examines the coating's composition, morphology, temperature-dependent dielectric properties, and corresponding electromagnetic wave attenuation characteristics. The permittivity exhibits a positive temperature dependence, which is primarily governed by the reduction in relaxation time and concomitant increase in electrical conductivity. The fabricated coating exhibits outstanding microwave absorption performance, which originates from conductive loss as well as interfacial and dipole polarization mechanisms. Notably, it demonstrates superior characteristics: an ultrathin thickness of merely 1.4 mm, high operating temperature up to 900 °C, and broad effective absorption bandwidths of 4.2 GHz (for RL < −5 dB) and 2.3 GHz (for RL < −10 dB). Simulation results reveal that the fabricated coating exhibits consistent radar cross section (RCS) values below −10 dBm² when subjected to temperatures above 200 °C, indicating promising characteristics for implementation as effective HTMACs in practical scenarios.