摘要多铁性材料通过铁电磁耦合作用会产生一些新的复合效应，具有极其重要的应用前景。BiFeO3是少数室温下同时具有铁电性和铁磁性的多铁性材料之一，但BFO的螺旋磁结构使其在低磁场下仅表现极弱的铁磁性。MnFe2O4（MFO）是一种尖晶石型晶体结构的磁性材料，其磁各向异性高、矫顽场大、电阻率高、化学性能稳定。利用固相反应法制取不同组份比例的尖晶石-钙钛矿混合相化合物，用以获得多铁性能更好的复合材料。其化学式为xMnFe2O4–(1–x)BiFeO3（其中x= 0.2,0.3,0.4或0.5），经X-射线衍射分析（XRD）和场发射扫描电镜分析（FESEM）等手段，分别研究其晶体结构和晶粒尺寸。其XRD的分析结果显示，xMnFe2O4-（1-x）BiFeO3（其中x=0.2, 0.3, 0.4, 0.5 ）样品的烧结温度在900℃-950℃之间，一次烧结和二次烧结都可以得到样品，但是二次烧结的效果更好。不同组分样品的最适宜烧结温度不同，MnFe2O4含量越高，相应的最是烧结温度越高，样品的晶粒尺寸越大，且在高频下，MnFe2O4的含量越高，样品的介电常数越大，介质损耗越小，电滞回线形状更好。而且样品还观察到标志着磁电耦合的磁电容。67802

毕业论文关键词  钙钛矿 尖晶石 MnFe2O4   BiFeO3  多铁性

毕业设计说明书（论文）外文摘要

Title   Dielectric properties of MnFe2O4-BiFeO3 multiferroic ceramics  

Abstract

The ceramics of xMnFe2O4–(1–x)BiFeO3 with x=0.2,0.3,0.4 and 0.5 were prepared by solid state reaction method. The structure and grain size were examined by means of X-ray diffraction and field emission scanning electron microscopy, respectively. The XRD results showed that the ceramics consisted of spinel MnFe2O4 and perovskite BiFeO3 phases after being calcined between the temperature 900℃ and 950℃.Either the one step method or the two step method were fine for calcining，but the two step method was found to be better. The grain size and the calcining temperature was found to increase with increasing concentration of MnFe2O4.The dielectric constant and the dielectric loss was also found to increase with increasing concentration of MnFe2O4 at high frequency. Magnetocapacitance was also observed in the prepared ceramics,which may be the sign of magnetoelectric coupling in the synthesized ceramics at room temperature.

Keywords  Spinel  Perovskites  MnFe2O4   BiFeO3 Multiferroic

目次

引言 5

1  材料呈现多铁性的原因 5

1.1  材料的铁电性 5

1.2  材料的铁磁性 8

1.3  铁电性与铁磁性共存 10

2  多铁性材料的种类 10

2.1  单相多铁性材料 10

2.2  复合多铁性材料 11

3  BiFeO3与MnFe2O4的复合多铁性材料 12

4  实验制备与性能测试 13

4.1  BiFeO3的制备 13

4.2  MnFe2O4的制备 13

4.3  xMnFe2O4-（1-x）BiFeO3系列样品的制备 14

4.4  性能测试 14

5  实验结果与分析 14

5.1  样品XRD的实验结果 14

5.2  样品电镜照片结果与分析