摘要近年来，多铁性材料由于同时具有铁电性、铁磁性甚至铁弹性等两种或两种以上基本铁性并且在这些铁序态之间存在磁电耦合等多种耦合效应而展现了丰富的物理内容，在新型传感器、自旋电子器件和高密度存储器件等方面具有广阔的应用前景。BiFe03(BFO)是到目前为止几乎唯一同时在室温以上表现出铁电性和铁磁性的材料，是最有希望得到应用的材料之一，但大的漏电流和弱的铁磁性等问题一直制约其发展和应用。大量研究表明，利用过渡金属对其进行B位掺杂，可有效的破坏空间调制自旋结构，减小陶瓷的漏电流，从而释放宏观磁化，提高材料的磁电效应。Mn4+离子半径略小于Fe3+，易进入Fe-O八面体。此外，其为3d轨道，易与O的2p轨道杂化，有效的增强铁电畸变，减少氧空位浓度。67173

 本课题利用快速烧结工艺制备BiFe1-xMnxO3 （x=0，0.025，0.05，0.075）系列陶瓷，后经XDR等分析手段，分析陶瓷的结晶性能，探讨合适的陶瓷烧结制度，并发现铁酸铋陶瓷的最佳烧结温度应为845℃附近。最后通过测量不同掺杂量下陶瓷样品的压电、介电性能，表明Mn可以取代晶格中Fe原子的位置，但当Mn掺杂量达到5%时MnO2就会过量，随着Mn掺杂铁酸铋晶体由三方晶系变为四方晶系。最佳的Mn掺杂量为2.5%,此时d33为37，另外，随着Mn掺杂，陶瓷的介电常数有增大的趋势，即电容有增大的趋势。

毕业论文关键词  BiFeO3陶瓷  多铁性  Mn4+掺杂   介电性能

毕业设计说明书（论文）外文摘要

Title    Study on The dielectric properties of Mn doped BiFeO3 ceramics                                   

Abstract

In recent years, Multiferroic materials, which show simultaneously ferroelectricity,ferromagnetism and/or even ferroelasticity, and the magnetoelectric coupling between the ferroic order parameters, have been in the forefront of materials research due to their interesting fundamental physics and potential applications in sensors, spintronics and information storage, etc.By far BiFeO3(BFO) may almost be the only material putting up ferroelectric property and magnetism simultaneity above the room temperature,which is one of the most promising material to be used.However,BFO becomes unsuitable for applications owing to its high leakage current and weak ferromagnetism.Numerous studies show that the use of transition metal doping its position B, the damage can be effectively spatially modulated spin structure, reducing the leakage current of the ceramic,thereby releasing macroscopic magnetization,the magneticelectric effect to improve the material. Mn4+ ionic radius smaller and Fe3+, easy to enter the Fe-O octahedron. In addition, it is 3d orbit, easy and O 2p orbital hybridization, effectively enhance the ferroelectric distortion, reduce the oxygen vacancy concentration.

In this thesis, the effects of ferroelectric properties of BiFe1-xMnxO3 (x = 0, 0.025, 0.05, 0.75,1) ceramics are investigated systematically. A rapid liquid-phase sintering method was applied to prepare single phase BiFe1-xMnxO3 ceramics. The structure of BiFe1-xMnxO3 ceramics were characterized by X-ray diffraction (XRD) using a Rigaku Ultima-iii diffractometer with Cu Kα radiation. loops of the ceramics X-ray diffraction results confirm that a phase transition from rhombohedral to tetragonal structure occurs at about 5% Mn substitution, which reveals that Fe2+ in the films can be suppressed by Mn substitution. Piezoelectricd33 value of un-doped BFO can be maintained when Mn concentration is less than 5%. With 2.5% Mn substitution, the ceramic shows a large d33 of 37.0pC/N.Meanwhile, Large ferroelectric remanent polarization of un-doped BFO can be maintained when Mn concentration is less than 5.0%. These results demonstrate that Mn doped BiFeO3 ceramics may be promising candidates for multifunctional applications due to the simultaneous exhibition of enhanced ferroelectric properties.