Study Of The Performance Of BiFeO₃ Materials A-site Doping Prepared By Polypropylene Sol-gel Method

Founding of multiferroic materials with magnetic effect makes it possible to design new memory. As the only room-temperature multiferroic material, BiFeO3 has magnetoelectric effect due to it shows ferroelectric ordering and ferromagnetic ordering, there are a wide range of application prospects. However, it still has some difficulties in practical applications. On the one hand, although BiFeO3 belongs to space group (R3c) and allows existing weak ferromagnetism, but it has a G-type antiferromagnetic structure, and shows 62 nm cycle of antiferromagnetic space spiral structure, its residual magnetism is very weak, this makes BiFeO3 hardly exhibit magneticon the macroscopic. On the other hand, due to the Bi elements is rerelatively easy to volatile during synthesis and Fe valence fluctuation, leading to he synthetic materials containing oxygen vacancies, Miscellaneous phase defects, makes it difficult to prepare pure phase BiFeO3 and there is a large leakage current, this series of problems have restricted the potential applications of this single-phase multiferroic materials.At present, there are many groups has studied the properties of BiFeO3 which was doped with an element on A-sites or B-sites, it turns out that doped on A/B-sites is an effective method to improvement the physical properties. However, there are little groups has studied the properties of BiFeO3 which was double doped with different elements only on A-sites or B-sites. In this paper, we have mainly study the ferroelectric-magnetic properties of BiFeO3 which was single doped by alkaline earth ions or double doped on A-sites. The main contents are as follows:1. Sr2+ ions was a substitute for Bi3+ ions, resulting in distortion of crystal structure system, it showed that the XRD diffraction peaks was merged. The scanning electron microscopy showed that when the doping amount x= 0.04 and calcination temperature is 600℃, it can get the best performance of Bi1-xSrxFeO3 nanoparticles, and higher purity, smaller particles size and better appearance can be obtained in this temperature.2. Through the XRD results of Bii-xCaxFeO3 nanoparticles known that due to ionic radius difference, the Ca2+ion can grain refinement. With increasing Ca2+ion concentrationthe sample magnetic was decreased, but the dielectric constant was increased with increasing Ca2+ion concentration, at the same time, the leakage properties of materials has also been improved.3. The measurement result of Bi0.8Ca0.2-xSrxFeO3 nanoparticles (x=0.04、0.10、0.13、0.17、 0.20) By Ca2+, Sr2+co-doped showing the crystal structure distortion leaded to diffraction peaks migrated to low angle, and the particle size decreased firstly and then increased in the solution with the increase of Sr2+ concentration, which indicates that the changes of concentrations of Ca2+, Si2+ in the sample is directly affects the grain growth situation. Along with the changes of Ca2+, Sr2+ concentration, originally highly helical structure was damaged and the sample magnetic was also released, eventually making the sample magnetic get promotion.