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采用快速液相烧结法制备BiFeO3和Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2)陶瓷样品,研究Gd, Co共掺杂对BiFeO3微观结构, 介电性能和铁磁性的影响. X射线衍射谱表明:所有样品的主衍射峰与纯相BiFeO3相符合且 具有良好的晶体结构,随着Co3+掺杂量x的增大, Bi0.95Gd0.05Fe1-xCoxO3样品的主衍射峰(104)与(110)逐渐相互重叠, 当x大于0.1时, 样品呈现正方晶系结构; J-V特性显示Gd3+, Co3+共掺杂有效地降低BiFeO3陶瓷的漏导电流,其降低幅度为1-2个数量级; 当f=103 Hz时, Bi0.95Gd0.05Fe0.8Co0.2O3的介电常数是BiFeO3的6倍, 而Bi0.95Gd0.05Fe0.95Co0.05O3和 Bi0.95Gd0.05Fe0.85Co0.15O3样品的介电损耗最小,均为0.01.室温下, Bi0.95Gd0.05Fe1-xCoxO3样品磁性与BiFeO3相比显著增强. 在磁场为30 kOe的作用下,Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2)的剩余磁化强度Mr分别是BiFeO3的34, 60, 105, 103, 180倍.样品磁性增强的主要原因是Gd, Co掺杂使BiFeO3的晶格结构发生变化导致BiFeO3自身储存的磁性能被释放, Gd3+的4f电子与Fe3+或Co3+的3d电子自旋相互作用及样品中存在局域的 Fe-O-Co磁耦合三者共同作用的结果.Multiferroic Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2) ceramics were prepared by rapid liquid phase sintering method. We studied effect of Gd and Co doping on the structure, electrical and ferromagnetism properties of BiFeO3 ceramics. The structure and morphology of BiFeO3 ceramics are characterized by X-ray diffraction (XRD). The results show that all the peaks for Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2) samples can be indexed according to the crystal structure of pure BiFeO3. And X-ray diffraction analysis reveals a phase transition in Gd-Co codoped BiFeO3 ceramics when x is larger than 0.1.The current densities of all samples measured at room temperature are approximately three orders of magnitude lower than that of BFO ceramic, and the leakage current of the ceramics at room temperature exhibits two distinctive conduction behaviors: Ohmic conduction and space charge limited (SCL) conduction mechanism.For all the samples studied here, the dielectric constant and dielectric loss decrease with the increase of frequency in a range from 1 kHz to 1 MHz. The dielectric constants of Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15,0.2) samples are nearly 1.9, 2.68, 3.85, 5.3, and 6 times larger than that of pure BiFeO3 (εr= 61.2) ceramic at 1 kHz, respectively. And the dielectric losses of Bi0.95Gd0.05Fe1-xCoxO3 samples become smaller than that of BFO ceramic.The magnetic measurements show that all the samples possess strong ferromagnetism at room temperature expect BiFeO3 and Bi0.95Gd0.05FeO3 which are weakly ferromagnetic. Under an external magnetic field of 30 kOe, the values of Mr of Bi0.95Gd0.05Fe1-xCoxO3 are 34, 60, 105, 103 and 180 times that of BiFeO3, respectively.
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Keywords:
- multiferroic/
- magnetic hysteresis loops/
- leakage current
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