Preparation And Properties Of Bismuth Layered Materials

Multiferroic materials have two or more ferroic ordering properties at the same time,such as ferroelectric,ferromagnetic,and ferroelastic,and the mutual coupling between multiple order parameters produces new effects.This kind of functional materials has huge application prospects in many fields such as detectors,sensors,information storage,electronic information functional devices,and microwave devices with dual magnetic and electric adjustments,etc.Multiferroic magnetoelectric materials not only have both ferroelectricity and ferromagnetism,but also have(inverse)magnetoelectric coupling effect,which can realize the regulation of electrical(magnetic)performance through the magnetic field(electric field).Compared with bulk magnetoelectric materials,with the development trend of miniaturization and multi-function of devices,magnetoelectric thin films have become a hot spot.In this study,a four-layer Aurivilius phase structure single-phase magnetoelectric material Bi₄Nd Ti₃Fe_0.5Co_0.5O₁₅(BNTFC)was constructed by inserting the multiferroic group Bi Fe O₃ into the three-layer Bi₄Ti₃O₁₂,and doping the rare earth ion Nd at the A site and the magnetic ion Co at the B site at the same time.Single-phase magnetoelectric thin film prepared by pulsed laser deposition(PLD)method,and composite it with single-phase ferroelectric film and single-phase ferromagnetic film,formation of 2-2 type heterostructure magnetoelectric composite film.The specific research content is as follows,(1)We prepared BNTFC,Ba Ti O₃(BTO),and La_0.8Sr_0.2Mn O₃(LSMO)ceramic targets using the traditional high-temperature solid-phase reaction method.The phase structure of the ceramic target was analyzed by X-ray diffractometer(XRD),and it was found that the diffraction peaks of all the targets corresponded well with the standard card.(2)The PLD method was used to prepare BNTFC single-phase films on(111)Pt/Ti/SiO₂/Si(100)substrates.The films were grown under different deposition temperatures,deposition pressures,and sputtering frequencies.The test and analysis of the microstructure and ferroelectric properties showed the best process for preparing single-phase films.and under these conditions,BTO and LSMO single-phase films were prepared.(3)Based on the preparation of BTO,LSMO single-phase films,the 2-2laminated structure BTO/BNTFC,LSMO/BNTFC composite films were prepared.The parameters,including phase structure,microstructure,piezoelectric properties,ferroelectric properties,leakage current characteristic,ferromagnetic properties,magnetoelectric properties of the films,were tested and analyzed.The magnetoelectric coupling phenomenon has been measured in the LSMO/BNTFC composite films,the magnetoelectric coupling coefficient?_E of which turns out to be4.30 m V/cm·Oe.