Enhanced microwave absorption and electromagnetic shielding property of (1-x)K0.5Na0.5NbO3 ~ xAl2O3 nano-ceramics

Abstract

(1-x) K0.5Na0.5NbO3 ~ xAl2O3 (x = 0, 0.2, 0.4, 0.6) ceramics were prepared via a traditional solid-state reaction method. The phase structure, micro-morphology, dielectric properties and electromagnetic properties of ceramic samples were studied and analyzed. Results indicate that all the samples are similar to K0.5Na0.5NbO3 (KNN) in perovskite structure. With the increase of Al2O3 content, the X-ray diffraction peaks move to a large angle region, suggesting the substitution of niobium ions by aluminium ions and the distortion of the KNN lattice with a new phase arising. With the increase of Al2O3 content the grain size reduces and the dielectric constant decrease, yielding to the decrease of the electromagnetic shielding performance of ceramic. When the x is 0.4, the minimum value of reflectivity of sample is −28 dB at the frequency of 11.6 GHz. It can be concluded that both the grain size and Al2O3 content can obviously affect the electromagnetic properties of ceramics, which can be easily turned through a multi-layer SiO2 heterojunction structure.