The influence of Ni-ion doping on the structure, magnetism, and electromagnetic wave absorption performance of La_0.6Sr_0.4Fe_1-xNi_xO_3-δ perovskite oxides

In the contemporary world, there is an urgent need for materials that are lightweight, have thin profiles, and can effectively absorb a wide bandwidth of electromagnetic waves (with a frequency f_E where the reflection loss RL ≤ −10 dB) while exhibiting strong attenuation capabilities. Such materials are essential for mitigating electromagnetic pollution in both military and civilian sectors. Perovskite oxides, known for their unique crystal structures and tunable ionic doping, have found extensive applications in photocatalysis, electrocatalysis, and electromagnetic wave absorption. This study systematically investigates the microstructure, magnetic properties, and electromagnetic wave absorption capabilities of La_0.6Sr_0.4Fe_1-xNi_xO_3-δ nanoparticles synthesized via the sol-gel method by co-doping Sr²⁺ and Ni²⁺ into LaFeO₃. X-ray diffraction analysis confirms that the nanoparticles possess a pure orthorhombic perovskite structure with notable lattice expansion. Scanning electron microscopy (SEM) reveals lattice distortion and crystal defects. The observed enhancements in specific surface area, alterations in the valence states of Fe and Ni ions, and changes in the levels of adsorbed oxygen and oxygen vacancies contribute to the shifts in magnetization and electromagnetic properties. Upon successful Ni doping, the sample with x = 0.1 exhibits an effective absorption bandwidth (EAB) of 4.67 GHz and a minimum reflection loss (RL_min) of −40.41 dB at f = 11.32 GHz (X-band) at a thickness of 1.5 mm. For x = 0.2, the RL_min is −58.36 dB at f = 15.3 GHz (Ku-band), with an EAB of 4.62 GHz at a thickness of 1.8 mm. Thus, optimal Ni ion doping significantly enhances the electromagnetic wave absorption performance of La_0.6Sr_0.4Fe_1-xNi_xO_3-δ nanoparticles, showing promise for applications in the X-band and Ku-band. Concurrently, the dual-ion co-doping of perovskite oxides, leveraging their unique crystal structure and superior performance, offers a promising avenue for the development of electromagnetic wave absorbing materials.