Study On The Magnetic And Dielectric Properties Of Bismuth Ferrite Nanomaterials By Substituted Doping

Bismuth ferrite ?BFO? is one multiferroic material presenting antiferromagnetism and ferroelectricity at room temperature. It has great potential of applications for sensors, storages and microwave absorption. Howener, because of the G-type spin structure of antiferromagnetic moment, the macro magnetism is very weak, thus hampering practical application of BFO.In this paper, we systematically investigated structure, magnetism, ferroelectricity and dielectric properties of single element doped ?Mg, Ca? and dual element co-doped ?Pr and Mg, Mg and Ca, La and Ni? BFO. Among them, the magnetization of Mg-substituted BFO is greatly improved, higher than other reported element-doped BFO at A site. The reason is attributed to the large radius difference between Mg²⁺ and Bi³⁺ ions. The tolerance factor of Mg-doped BFO is on the edge for the stabilization of perovskite structure, and then it leads to large distortion of the antiferromagnetic structure, resulting in the realease of the offsetted magnetic moment in a great scale. Moreover, the pinning effect of MgBi'-Vo" dipole on oxygen vacancy decreases the leakage current, which improves the ferroelectricity of Mg-doped BFO at 2mol% doping level. Considering that Pr has 6s2 lone pair electrons, Pr and Mg elements co-doped BFO materials were prepared to obtain further improved ferroelectricity. As expected, compared with Mg-doping at 2mol% doping level,3mol% Pr and 2mol% Mg co-doping brings about both higher ferromagnetism and ferroelectricity, which make the material a candicate in sensors and storages. As for La and Ni co-doped BFO, the magnetization is higher than that of Pr and Mg co-doped BFO at the same doping level, which is due to the superexchange interaction between Ni²⁺ and Fe³⁺ ions. Ca-doped BFO and Mg, Ca co-doped BFO show higher conductivity, dielectric constant and dielectric loss in X band. Moreover, two absorption peaks are observed in these materials. Here,5mol% Ca-doped BFO exhibits an absorption band as high as 3.4 GHz at the thickness of 1.56mm, which has remarkable advantage in practical application of ultrathin and broadband microwave absorption.