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摘 要众所周知，多铁材料很难在室温下保持良好的铁电性和磁性，而 BiFeO3的铁电居里温度和反铁磁的奈尔温度都远远高于室温， 在室温下铁电和铁磁即可实现耦合作用和相互调控，因此有着巨大的应用潜力。然而纯相的 BiFeO3由于具有 G 型反铁磁结构，呈现周期性的反铁磁螺旋结构，剩余磁性比较相较于其他铁磁性材料较弱。为减少材料中含有氧空位等缺陷，提高铁酸铋的铁电性和实用性，通常采用Bi 位的稀土元素掺杂。因此本论文利用在 Bi 位进行稀土元素掺杂从而改善纯相铁酸铋陶瓷的性能，通过对掺杂样品的晶体结构、微观形貌、铁磁性和介电性的测试，分析不同稀土元素掺杂对BiFeO3陶瓷性能的影响。本文通过溶胶凝胶法，制备了掺杂 La, Sm, Gd, Y 的 BiFeO3陶瓷，将合成的Bi0.8M0.2FeO3 （M= La, Sm, Gd, Y） 纳米粉体材料通过压片、 烧结的方法得到黑色、硬度和致密度很高的陶瓷材料，同时利用 X 射线衍射仪(XRD)、扫描电子显微镜(SEM)观察了陶瓷的物相组成和显微结构，并且利用振动样品磁强计和阻抗测试仪对掺杂后的铁酸铋陶瓷铁磁和介电等性能特性进行表征。结果如下：（1） XRD 谱表明掺杂稀土元素制备出的改性Bi0.8 M0.2FeO3陶瓷材料为钙钛矿结构，但仍出现一些杂质相。相比于纯相 BiFeO3陶瓷，在所掺杂的 Bi0.8 M0.2FeO3陶瓷中，掺杂之后更容易得到单相的钙钛矿结构。此外 SEM 图像显示，Bi0.8M0.2FeO3微观组成较为致密，晶粒尺寸较小。（2）将合成的Bi0.8M0.2FeO3陶瓷圆片，使用 Agilent 4294A 阻抗测试仪测试了样品圆片的介电常数。通过测得数据分析可知，随着掺杂离子半径的增大掺杂铁酸铋的介电常数逐渐降低。利用振动样品磁强计(VSM)测量样品的磁学性质，结果表明随着掺杂元素的原子半径大小的增加，比饱和磁化强度（Ms）逐渐减小，而矫顽力（Hc）则呈现不断增大的趋势。（3）通过在 Bi位掺杂稀土元素的 Bi0.8M0.2FeO3陶瓷能够有效的抑制氧空位的产生，进而增强介电极化，并且增强磁性。58982
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毕业论文关键词：溶胶-凝胶法；多铁性材料；BiFeO3陶瓷；掺杂La
Abstract As we all know, it’s difficult for multiferroic materials to keep in betterferroelectric and magnetic properties at room temperature. BiFeO3 ferroelectric Curietemperature and temperature of antiferromagnetic Cornell are far higher than theroom temperature, at room temperature ferroelectric and ferromagnetic coupling andregulation can be realized, it has great potential. However pure phase of BiFeO3, withg-type antiferromagnetic structure periodically antiferromagnetic structurecomparison compared to other magnetic ferromagnetic materials remaining weak. Toreduce material containing oxygen vacancies and other defects, increase offerroelectric bismuth ferrite and practicality, usually in Bi-doped with rare earthelements. This paper used in Bi-doped with rare earth elements to improve theperformance of phase-pure bismuth ferrite ceramic, through doping samples of crystalstructure and microstructure, magnetic and dielectric properties of iron test, analyzethe impact of different rare earth doped BiFeO3 properties.Paper through sol gel rubber method, preparation has doping La, Sm, Gd, y ofBiFeO3 ceramic, will synthesis of Bi0.8M0.2FeO3 (M= La, Sm, Gd, Y) nanopowderbody material through pressure tablets, and sintering of method get black, andhardness and dense degrees is high of ceramic material, while using x ray diffractioninstrument (XRD), and scan electronic microscope (SEM) observation has ceramic ofreal phase composition and micro structure, And the use of vibrating samplemagnetometer and impedance Tester on iron-doped bismuth ferrite ceramic magneticand dielectric characterization of performance characteristics such as. Results are asfollows:(1) The XRD spectra show that the modified Bi0.8M0.2FeO3 ceramics doped withrare earth elements prepared materials for the perovskite structure, but there are stillsome impurities. Compared to the pure phase BFO, Bi0.8M0.2FeO3 ceramics doped,doped perovskite structure easier to obtain clean after. Also SEM image showsBi0.8M0.2FeO3 micro-composition is compact, small grain size and lattice constant. (2) Synthetic Bi0.8M0.2FeO3 ceramic wafer, using the Agilent 4294A impedanceTester sample wafers of dielectric constant. By measured data analysis, with dopedbismuth ferrite doped with ionic radii increase of dielectric constant gradually reduces.Vibrating sample magnetometer (VSM) measurement of the magnetic properties ofthe sample, results show that with the increase in Atomic radius size of dopingelements than the saturation magnetization (Ms) decreases, and coercive force (Hc)show a growing trend.(3) In Bi-doped rare-earth element of Bi0.8M0.2FeO3 ceramic effectively inhibitsoxygen vacancies and enhance the dielectric polarization, and magnetic.