Strong microwave absorption observed in dielectric La1.5Sr0.5NiO4 nanoparticles

TL;DR

This study demonstrates that La1.5Sr0.5NiO4 nanoparticles exhibit strong microwave absorption in the 4-18 GHz range, making them promising for radar absorbing materials due to impedance matching effects.

Contribution

The paper reports the synthesis of La1.5Sr0.5NiO4 nanoparticles and their effective microwave absorption properties, highlighting impedance matching as the key mechanism, which is a novel insight.

Findings

Strong microwave absorption observed in 4-18 GHz range.

Absorption strength depends on layer thickness, reaching -36.7 dB.

Impedance matching, not phase matching, drives resonance.

Abstract

La$_{1.5}$Sr$_{0.5}$NiO$_4$ is well known to have a colossal dielectric constant ($\varepsilon_R>10^7$). The La$_{1.5}$Sr$_{0.5}$NiO$_4$ nanoparticle powder was prepared by a combinational method of solid state reaction and high-energy ball milling. Magnetic measurements show that the material has a very small magnetic moment and paramagnetic characteristic at room temperature. The mixture of the nanoparticle powder (40% vol.) and paraffin (60% vol.) coated in the form of flat layers of different thicknesses ($t$) exhibits strong microwave absorption resonances in the 4-18 GHz range. The reflection loss ($RL$) decreases with $t$ and reaches down to -36.7 dB for $t=3.0$ mm. The impedance matching ($|Z|=Z_0=377$ $\Omega$), rather than the phase matching mechanism, is found responsible for the resonance observed in the samples with $1<t\leq3.0$ mm. Further increase of the thickness leads to $|Z|>Z_0$ at all frequencies and a reduced absorption. The influence of non-metal backing is also discussed. Our observation suggests that La$_{1.5}$Sr$_{0.5}$NiO$_4$ nanoparticles could be used as good fillers for high performance radar absorbing material.