多铁性材料是近年来兴起的一种新的磁电功能性材料，能够同时表现出铁电性和铁磁性，并且在铁磁性和铁电性之间会发生耦合效应，因而多铁性材料在信息存储、自旋电子器件、磁传感器以及微波技术等领域有着极其广泛的应用前景。但是，在目前已发现的单相多铁性材料中，大多数材料只能在较低的温度下才能同时表现出铁磁性、铁电性和磁电耦合效应。M型六角铁氧体是一种很典型的磁性材料，它的分子通式是AB₁₂O₁₉,式中：A为Ba、Sr、Pb等半径较大的离子， B为Fe³⁺ 离子，或者是半径与Fe³⁺离子半径相接近的其它三价阳离子，整个结构属于六角菱形晶系，所以一般称之为六角铁氧体。近年来，随着材料技术的蓬勃发展，特别是在材料多铁性能上的研究，六角铁氧体逐渐表现出重要的研究价值。本课题组根据多铁性材料研究现状探索新型多铁性材料，通过改善实验方案和利用稀土元素取代方法制备M型六角铁氧体，并实现其在室温下的多铁性和磁电效应。本论文研究了两种M型六角铁氧体的多铁性，通过稀土元素取代对其中一种铁氧体材料进行了改性，主要内容和结果如下：

1. SrFe₁₂O₁₉ 陶瓷的制备及多铁性研究

采用聚合物前驱体溶液法合成制备得到了SrFe₁₂O₁₉ 粉体，通过陶瓷制备工艺将上述得到的粉体制备出了SrFe₁₂O₁₉ 陶瓷，接着对陶瓷样品进行了氧气热处理，得到最终样品。通过XRD图谱可以清楚地分析出SrFe₁₂O₁₉ 粉体的物相组成；室温下的铁电测试以及铁磁测试表明SrFe₁₂O₁₉样品表现出良好的铁电性与铁磁性，并且氧处理使得样品的电滞回线不再是“香蕉型”，而是趋于饱和，剩余电极化强度为57.66µC/cm²，矫顽电场强度为10.10kV/m，剩余磁极化强度为32.37emu/g，矫顽磁场强度为5590Oe，相比于未经氧处理的SrFe₁₂O₁₉材料，剩余电极化强度提高了3.8倍，矫顽磁场强度提高了1.3倍；介电性能测试表明SrFe₁₂O₁₉样品是良好的弛豫铁电体，温度上升过程中，介电常数在相变温度附近的变化符合居里-外斯定律。在磁电效应方面，SrFe₁₂O₁₉陶瓷表现出磁电容效应， [ε(B)-ε(0)]/ε(0)%的最大值约为1170%。由实验数据可得，SrFe₁₂O₁₉ 陶瓷材料是一种良好的单相多铁性材料，并且氧气热处理这一步骤对于提高SrFe₁₂O₁₉材料的多铁性有很大作用。

2. La_0.2Pb_0.7Fe₁₂O₁₉ 陶瓷的制备及多铁性研究

采用稀土元素取代的方法，向前驱体溶液中加入La(NO₃)₃的水溶液，合成得到了La_0.2Pb_0.7Fe₁₂O₁₉ 粉体。通过陶瓷制备工艺将上述粉体制备出了La_0.2Pb_0.7Fe₁₂O₁₉ 陶瓷，然后对陶瓷进行氧气热处理，得到最终样品。通过XRD图谱可以清楚地分析出La_0.2Pb_0.7Fe₁₂O₁₉ 粉体的物相组成；室温下的铁电测试以及铁磁测试表明La_0.2Pb_0.7Fe₁₂O₁₉样品在室温下具有良好的铁电性和铁磁性，并且得到的标准型电滞回线以及I-V曲线中的两个非线性特殊峰，证明了La_0.2Pb_0.7Fe₁₂O₁₉陶瓷的铁电性是由于其自身的极化而产生； La_0.2Pb_0.7Fe₁₂O₁₉陶瓷样品的介电性能测试表明实验制备得到的La_0.2Pb_0.7Fe₁₂O₁₉陶瓷是良好的弛豫铁电体，并进一步证明了La_0.2Pb_0.7Fe₁₂O₁₉材料的本征铁电性。掺杂取代改性之后的La_0.2Pb_0.7Fe₁₂O₁₉材料的剩余极化强度为132.25μC/cm²，矫顽电场强度为19.8kV/m，剩余磁极化强度为30.1emu/g，矫顽磁场强度为3439.2Oe，相比于PbFe₁₂O₁₉材料，La_0.2Pb_0.7Fe₁₂O₁₉的剩余电极化强度提高了1.27倍，矫顽电场提高了1.3倍，矫顽磁场提高了1.48倍。在磁电效应方面，La_0.2Pb_0.7Fe₁₂O₁₉陶瓷不但表现出磁电耦合效应，同时也表现出巨磁电容效应，耦合电压最大为26.5mV，[ε(B)-ε(0)]/ε(0)%的最大值约为190000%。

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