Microwave absorption properties of La1.5Sr0.5NiO4-based nanocomposites

La1.5Sr0.5NiO4 is a well-known dielectric with colossal dielectric constant but a superparamagnet-like material with tiny magnetization. Mixing La1.5Sr0.5NiO4 with high permittivity ferrimagnets or ferromagnets is expected to modify the dielectric-magnetic balance and enhance the magnetic loss in the microwave absorption capability. In this work, dielectric La1.5Sr0.5NiO4 and soft ferromagnetic La0.7Sr0.3MnO3 nanoparticles were prepared by a combination method of solid-state reaction and high-energy ball milling. The microwave absorption properties of (100-x)La1.5Sr0.5NiO4/xLa0.7Sr0.3MnO3 nanocomposites mixed in paraffin were studied. The optimal microwave absorption is obtained for x = 4 with the reflection loss (RL) reaches down to −28.5 dB. The impedance (Z) matching resonance shifts to lower frequencies with increasing x, in contrast to what observed in (100-x)La1.5Sr0.5NiO4/xNiFe2O4. The results suggest that beside the modification of Z by the dielectric-magnetic balancing, the coupling among the nanoparticles plays a major role in governing the microwave absorption properties of the composites. We also verify that the phase matching resonance that produces a zero total reflection from the absorber can be greatly improved when the sample is attached on a metal plate. •(100-x)La1.5Sr0.5NiO4/xLa0.7Sr0.3MnO3 nanocomposites have been prepared for microwave absorption.•The maximum RL of -28.5 dB at resonance frequency 13.6 GHz is obtained for x = 0.4.•The impedance matching and phase matching resonances are observed.•The phase matching resonance is enhanced in samples with metal backing.