Preparation And Microwave Absorption Performance Of Lanthanum Perovskite-based(ABO₃) Oxide Materials

Currently,electromagnetic wave(EMW)pollution has become a novel environmental pollution due to the extensive utilization of electronic and communication technology.In order to solve these problems,many efforts have been dedicated to develop the high-performance microwave absorbing materials possessing advantages of lightweight,thickness,strong absorption and broad frequency bandwidth.Therefore,numerous microwave absorption materials have been investigated taking into account their outstanding dielectric and magnetic characteristics.Up to now,only a small amount of perovskite oxide materials have been developed and applied in electromagnetic microwave absorption.Therefore,based on the current research status of the electromagnetic microwave absorption properties of perovskite oxide,this paper carried out the synthesis and wave absorption properties of several perovskite oxide materials(ABO₃).1.The lanthanum doped barium stannate nanoparticles have been fabricated facially via a wet chemical reaction and subsequent annealing process.The thermal decomposition,phase purity,morphology,microstructure and microwave absorption are characterized by TG-DSC,XRD,FESEM,TEM and VAN.The results reveal that the Ba_1-xLa_xSn O₃(x=0.02,0.04 and 0.06)nanoparticles exhibited enhancement of microwave absorption performance compared with the pure BaSn O₃.The reason is that La³⁺ions replace Ba²⁺ions which the number of electrons entering the conduction band increases with the increase of doping concentration,the electrical conductivity of barium stannate nanoparticles increases.On the other hand,with the doping of La³⁺ions,the lattice of BaSn O₃ nanoparticle distorts which causes a strong polarization effect,which is conducive to the improvement of microwave absorption performance.For the sample of Ba_0.98La_0.02Sn O₃,the minimum reflection loss reaches-43.78 d B at the thickness of 1.5 mm and the effective absorption bandwidth reaches 3.12 GHz(12.24-15.36 GHz).2.LaNiO₃ microspheres have been synthesized by a simple hydrothermal synthesis and subsequent annealing process.The LaNiO₃microspheres are characterized by TG-DSC,XRD,FESEM,TEM and VAN.Noticeably,owing to the effective synergism between significant dielectric loss and optimum impedance match,LaNiO₃ microspheres exhibit significantly remarkable attenuation capability and wide-band response.A minimum reflection loss intensity-30.6 d B of LaNiO₃microspheres can be achieved and a broad effective absorbing bandwidth of 4.72 GHz(8.16-12.88 GHz)at the thickness of 2.0 mm.Furthermore,the overall effective bandwidth is obtained up to 14.5 GHz from 3.5 GHz to 18 GHz,covering more than90%of the measured frequency range.3.Perovskite oxide LaCoO₃ thin sheets have been obtained by hydrothermal synthesis and subsequent annealing process.Then,cation deficiency is introduced to the A-site of LaCoO₃ via a selectively etching strategy by Fe Cl₃ solution.The phase characteristics,morphologies,structures and microwave absorption performance of LaCoO₃ thin sheets with A-site cation deficiency have been systematically investigated.The results indicate that suitable introduces the A-site cation deficiency is beneficial to induce more dipoles polarization,leading to the boosted of the microwave absorption performance.When the mass of Fe Cl₃ is up to 0.3g,the LaCoO₃ thin sheets exhibited superior reflection loss characteristics in the range of test frequency.A minimum reflection loss value of-56.9 d B at 15.1 GHz can be achieved with a thin thickness of 2.0 mm.Meanwhile,a broad effective absorption bandwidth reaches 5.9 GHz,covering the range of 12.1-18.0 GHz.