Dielectric and microwave absorption properties of LaSrMnO₃/Al₂O₃ ceramic coatings fabricated by atmospheric plasma spraying

In this paper, LaSrMnO₃/Al₂O₃ ceramic coatings, intended as electromagnetic wave absorbers were fabricated by atmospheric plasma spraying (APS) technique with an internally fed powder torch. The LaSrMnO₃/Al₂O₃ composite powders were agglomerated by spray-drying technology. Morphology of the composite powders and cross-section of the coatings were revealed by scanning electron microscope (SEM). The effects of LaSrMnO₃ (LSM) content on dielectric properties and microwave absorption properties of the coatings were investigated in the frequency range of 8.2-12.4 GHz. The results indicated that both the real (ε′) and imaginary (ε″) parts of the complex permittivity increased with increasing LSM content. The relaxation polarization and interfacial polarization in the coatings would contribute to enhance ε′, and the conductance loss could be considered as a dominating factor for enhancing ε′. The calculation of the microwave absorption as a single-layer absorber shows that reflection loss values exceeding -10 dB can be obtained in the frequency range of 10.5-12.4 GHz when the LSM content is 80wt% and the coating thickness is only 1.5 mm.