Study on effect of doping content on the microstructure, dielectric and microwave absorption properties of x-NiO/CaMn_1−xO₃

By using a simple solid-phase sintering method, x-NiO/CaMn_1−xO₃ particles have been synthesized. The microstructure and electromagnetic properties of samples were characterized to analyze their microwave absorption performance in 8.2–18 GHz. The result indicates that the microwave absorption properties of CaMnO₃ can be efficiently improved and controlled by doping Ni ion at Mn-site with different content. The S3 (0.15-NiO/CaMn_0.85O₃) exhibits the optimum absorbing properties that the EAB reached 4.8 GHz (11.3–16 GHz) with a matching thickness of 1.8 mm. The enhanced microwave absorption properties originate mainly from dielectric loss. An amount of Ni ions infiltrated into the crystal lattice of CaMnO₃ causing the lattice distortion and other defects. The lattice distortion and other defects enhanced the polarization effects and relaxation effects of the samples leading to the change of dielectric loss. This study has provided an available approach to achieve CaMnO₃ materials with excellent microwave properties, including lightweight, strong reflection loss, and broadband absorption.