Effects of La3⁺ or Ti4⁺ doping on dielectric and microwave absorption performance of CaMnO3 in the 8.2–18 GHz

In this paper, CaMnO₃ and Ca_0.97La (or Ti)_0.03MnO₃ powders were synthesized using mechanical ball milling technique and sintered at 1100°C for 12 h in an air atmosphere. Results showed that all the samples are single phase with an orthorhombic symmetry. Compared with the pure CaMnO₃ sample, the Ca_0.97La_0.03MnO₃ and Ca_0.97Ti_0.03MnO₃ samples have higher complex permittivity and better microwave absorbing properties. These changes are caused by the doping-ion incorporating in CaMnO₃ lattice and Ca vacancies, which could result in abundant dipoles and the local charge accumulation. The Ca_0.97Ti_0.03MnO₃ sample exhibited the best microwave absorption performance, i.e. the minimum reflection loss was -46.9 dB with a matching thickness of 2.2 mm and effective absorption bandwidth reached 5.2 GHz with a thickness of only 1.8 mm. This study demonstrates that the CaMnO₃ would be a potential material in the microwave absorbing field and needs further research.