Preparation And Properties Of Lead-free Magentoelectric Composite Thin Films

Multiferroic magnetoelectric composite materials is a family of materials that the ferroelectricity and ferromagnetism exist simultaneously. Multiferroic materials not only have a single ferroelectricity or ferromagnetism, but also can produce magnetoelectric coupling effects by the coupling of the ferroelectric and ferromagnetic. This performance greatly enrichs the application of multiferroic materials. In recent years, the multiferroic magnetoelectric composite materials appeal more researchers’ attention and provoke a great number of research activities. Therefore, multiferroic materials have a wider application propect in the many fields such as magnetic sensor, information storage and Magnetoelectric dual regulation of microwave devices. In this dissertation, firstly, the author prepared SrRuO₃（SRO）、Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃（BCTZ） and NiFe₂O₄（NFO） ceramic targets with high density by the traditional high temperature solid state reaction method. Then, BCTZ/SRO and NFO films were prepared by pulsed laser deposition（ PLD） method. We investigated and optimized the preparation progress of excellent ferroelectric film and ferromagnetic film. This has laid the foundation for the subsequent preparation of composite films. Then the structure and properties of the composite films were studied systematically. The main research contents are as follows:1. Preparation of the SRO, BCTZ and NFO targets and the characterization of the structure.The high density of SRO, BCTZ and NFO ceramic targets were prepared by the traditional high temperature solid state reaction method. By means of X-ray diffraction（ XRD）, we analyzed the phase structure of the ceramic targets. We found that the preparation of ceramic targets orientation are consistent with the standard card, no impurity phase is formed.2. Preparation of the BCTZ thin film and the characterization of the structure and ferroelectricity.PLD method was used for depositing BCTZ thin film on a SrTiO₃（STO）（100） substrate with thin SRO electrode. Through testing and analyzing the microstructure and ferroelectric properties of BCTZ thin films, the optimal process parameters of the preparation of ferroelectric layer are obtained.3. Preparation of the NFO thin film and the characterization of the structure and ferromagnetism.PLD method was used for depositing NFO thin film on a STO（ 100） substrate. Through testing and analyzing the microstructure and ferromagnetic properties of NFO thin films, the optimal process parameters of the preparation of ferromagnetic layer are obtained.4. Preparation of the BCTZ/NFO magnetoelectric composite thin film and the characterization of the structure, ferroelectricity and ferromagnetism.PLD method was used for depositing 2-2 type magnetoelectric composite thin film. Through testing and analyzing the electric and magnetic properties of the composite thin films, the optimal process parameters of the preparation of ferromagnetic layer are obtained. The results show that the composite thin film has good ferroelectric and ferromagnetic properties.