Thin La doped CaMnO3 ceramics for attenuation-impedance balance to facilitate excellent microwave absorption

The perovskite structure oxide, CaMnO3, has been extensively investigated and applied as a potential microwave absorption material due to its versatile dielectric and spontaneous polarization. However, the low conductivity of pure CaMnO3 material limits its further application. Herein, to increase dielectric loss and achieve better microwave absorption properties, lanthanum (La)-doped CaMnO3 (Ca1-xLaxMnO3) ceramics were fabricated by a high temperature solid state reaction. The results of XRD and XPS show that the La atom was efficiently doped at the Ca site in CaMnO3, which carries excess positive charges and affects the valence state of Mn ions and the concentration of oxygen vacancies. Therefore, the conductivity and imaginary permittivity of Ca1-xLaxMnO3 ceramics increased dramatically with La-doped content. Benefiting from the tunable dielectric and impedance properties, Ca1-xLaxMnO3 ceramics can be utilized in a highly efficient way to absorb microwave radiation with a thin thickness. The sample with x = 0.04 shows the best microwave absorption property, with an RLmin value of -52.63 dB (d = 1.41 mm) and effective absorption bandwidth coves full X band in the thickness range from 1.315 mm to 1.395 mm.