铋系层状钙钛矿铁电体的磁性掺杂及多铁性能研究

发布时间：2019-06-10 03:10

【摘要】：单相多铁材料是指同时表现出铁电性和磁性的单相化合物。由于单相多铁材料中铁电性和磁性原子层面的组合可实现磁电耦合量子调控,与那些传统的磁性材料或铁电材料相比,具有磁电耦合效应的单相多铁材料在新型信息存储及磁电器件等方面有巨大的应用潜力。本论文的核心工作是从磁性掺杂的角度,对三层及四层铋系层状钙钛矿结构的铁电体进行系统的材料改性工作,实现了样品在室温下铁电性和铁磁性的共存,发现磁性元素对Bi4Ti3O12(BTO)及Bi5Ti3FeO15(BTF)陶瓷样品的磁改性规律,并初步探索了磁性元素掺杂对BTO及BTF材料多铁性影响的内在机制及铁电性和铁磁性互相耦合调控的微观物理机制。具体分为下面几个部分： (1)研究了磁性元素A位或B位掺杂三层钙钛矿BTO的室温多铁性随掺杂含量的变化规律及部分样品的室温磁电耦合效应。采用传统固相反应法制备A位掺杂Bi3.15-xNixNd0.85Ti3O12,Bi3.15-xMnxNd0.85Ti3O12-δ和B位掺杂Bi4FexTi3-xO12-δ Bi3.15Nd0.85NixTi3-xO12-δ, Bi3.15Nd0.85MnxTi3-xO12,Bi3.15Nd0.85CoxTi3-xO12-δ六个系列陶瓷样品。不论是A位还是B位掺杂,磁性离子均成功进入到类钙钛矿层中相应的位置；其中A位或B位掺Ni和Mn的样品磁滞回线呈线性,室温磁性较弱,而Fe和Co的B位掺杂使得样品的磁滞回线呈现典型的铁磁“S”型,在掺Fe系列x=2样品中,观察到了较明显的室温磁电耦合。对于磁性增强的内在机制及磁电耦合机理,论文做了详细的讨论分析。 (2)探讨了B位磁共掺杂三层钙钛矿Bi3.15Nd0.85Ti3O12(BNT)的磁性增强的内在机制及室温正磁电容效应的微观物理机制。采用传统固相法制备得到(Bi3.15Nd0.85)(Ti2FexCo1-x)012-δ样品。实验发现,样品仍具有三层钙钛矿结构；与(1)中样品相比,Fe和Co的共同掺杂虽同样增加了样品的漏流,但大大改善了样品的磁性能。XPS价态分析结果表明,样品中Fe3+与Fe2+共存。结合价态分析的结果,论文分析讨论了样品磁性增强的内在机制；在x=0.5样品中还观察到了较大的正磁电容效应,当测试频率为30kHz时,磁电容约为14.2%,而且磁电容效应在低频区较为显著。 (3)研究了磁性元素的掺杂对四层钙钛矿BTF的磁改性机理。深入研究了由传统固相法制备的BTF、Bi5Ti3Fe0.5Ni0.5O15(BTFN)和Bi4NdTi3Fe0.5Co0.5O15(BNTFC)三组陶瓷样品的微观结构及各项性能。各样品均形成四层钙钛矿结构,介电常数存在较强烈的介电色散,样品铁电性能优良,与未掺BTF相比,Ni的B位掺杂、Nd的A位掺杂和Co的B位掺杂,确实改善了样品的室温铁磁性,论文从离子半径差及样品中存在的可能耦合两个方面分析了磁性增强的内在机制。 (4)系统研究了B位磁掺杂Bi4NdTi3(Fe1-xMx)O15(M=Nk、Mn、Cr和Co)系列陶瓷样品的室温多铁性,发现了“f0.3”现象,并对该现象出现的内在物理机制进行了初步探讨。采用改进固相法制备了磁性元素Ni、Mn、Co和Cr掺杂的BNTF系列样品。各系列样品均形成了四层钙钛矿结构,其中掺Co和Cr的样品为单相结构,而在掺Ni和Mn的样品中有少量氧化物出现。每个系列样品的磁滞回线均呈现典型的铁磁“S”型,除了Cr对样品磁性能改善较小外,其余三个系列的样品,在本文实验范围内,均当“x=0.3”时,样品的磁性能最佳。论文从不同磁性离子的浓度比例和磁性离子掺杂位置的角度,对该现象出现的内在物理机制进行了探讨。对于室温多铁性能较佳的掺Ni和掺Co“x=0.3”样品,我们进行了室温磁电耦合的表征,当测试电场较小时,与测试电场同步施加的外磁场使得这两个样品均表现出了室温磁电容效应；当测试电场较大时,与测试电场同步施加的外磁场增加了掺Ni样品的Pr和Ec的值。本论文的主要创新点如下： 1.在三层钙钛矿铁电体BTO中,寻找到了本文实验范围内的最佳磁改性方式,即B位磁性元素共掺杂。采用B位Fe和Co磁共掺杂,当Fe:Co=l：l时,样品具有最佳的室温多铁性,并且观察到了巨大的室温正磁电容效应。 2.在本文四层钙钛矿铁电体BTF磁掺杂改性工作中,发现了“x=0.3”现象,即当Fe：M≈7：3时(M为掺入的磁性离子),样品的磁改性效果最佳；不仅如此,在“x=0.3”样品中,也可以观察到较明显的磁电耦合现象。
[Abstract]:The single-phase multi-iron material refers to a single-phase compound that exhibits both ferroelectric and magnetic properties at the same time. due to the combination of the ferroelectricity and the magnetic atomic layer in the single-phase multi-iron material, the magnetoelectric coupling quantum control can be realized, compared with those of the traditional magnetic materials or the ferroelectric materials, The single-phase multi-iron material with magnetoelectric coupling effect has great application potential in new information storage and magnetoelectric device. The core work of this thesis is to carry out the material modification of the ferroelectrics of the layered perovskite structure of three layers and four layers in the aspect of magnetic doping, and realize the coexistence of the ferroelectricity and the ferromagnetism at room temperature. The magnetic modification of the magnetic elements on the Bi4Ti3O12 (BTO) and the Bi5Ti3FeO15 (BTF) ceramic samples is found. The internal mechanism of the influence of the doping of the magnetic element on the BTO and the BTO material and the micro-physical mechanism of the mutual coupling and control of the ferroelectric and the ferromagnetic are also studied. It is divided into the following parts: (1) The changes of the temperature of the three-layer perovskite BTO doped with the magnetic element A or B and the temperature and magnetoelectric coupling effect of some samples at room temperature were studied. The preparation of the A-site doped Bi3.15-xNixNd0. 85Ti3O12, Bi3.15-xMnxNd0.85Ti3O12-1 and B-position-doped Bi4FexTi3-xO12-1, Bi3. 15Nd0.85MnxTi3-xO12, Bi3. 15Nd0.85CoxTi3-xO12-6 series of ceramic samples was prepared by conventional solid-phase reaction. The magnetic ions all enter the corresponding position in the perovskite-like layer. The magnetic hysteresis loop of the samples with the A-or B-position is linear and the room-temperature magnetism is higher. Weak, and the B-position doping of Fe and Co causes the magnetic hysteresis loop of the sample to present a typical ferromagnetic "S" type. In the Fe-doped x = 2 sample, it has been observed that a significant room temperature magnetoelectric coupling is observed In this paper, the internal mechanism of magnetic enhancement and the mechanism of magnetoelectric coupling are discussed in detail. In this paper, the intrinsic mechanism of magnetic enhancement of B-position magnetic co-doped three-layer perovskite Bi3. 15Nd0.85Ti3O12 (BNT) and the microstructure of the positive magnetic capacitance effect at room temperature are discussed. The method is prepared by the conventional solid-phase method (Bi3. 15Nd0.85) (Ti2FexCo1-x)012- The sample still has a three-layer perovskite structure. Compared with the sample in (1), the co-doping of Fe and Co increases the leakage of the sample, but greatly improves the sample. The results of the analysis of the valence state of the XPS indicate that the Fe 3 + and the Fe 2 in the sample In combination with the results of the valence state analysis, the intrinsic mechanism of the magnetic enhancement of the sample is discussed. The larger positive magnetic capacitance effect is also observed in the x = 0.5 sample. When the test frequency is 30 kHz, the magnetic capacitance is about 14.2%, and the magnetic capacitance effect is lower in the low frequency region. The doping of the magnetic element on the four-layer perovskite BTF was studied. The microstructure of three groups of ceramic samples of BTF, Bi5Ti3Fe0.5Ni0.5O15 (BTFN) and Bi4NdTi3Fe0.5Co0.5O15 (BNTFC) prepared by the traditional solid-phase method were studied. And all the samples form a four-layer perovskite structure, the dielectric constant has a strong dielectric dispersion, the sample ferroelectric performance is excellent, the B-position doping of the Ni, the A-position doping of the Nd and the B-position doping of the Co are improved compared with the non-doped BTF, and the sample is indeed improved. The magnetic enhancement is analyzed in terms of the difference of the ionic radius and the possible coupling in the sample at room temperature. The internal mechanism of B-position magnetic-doped Bi4NdTi3 (Fe1-xMx) O15 (M = Nk, Mn, Cr and Co) series of ceramic samples was studied in the system. The "f0.3" phenomenon was found and the intrinsic physical mechanism of the phenomenon was investigated. The magnetic elements Ni, Mn, Co and Cr-doped B were prepared by the modified solid-phase method. The NTF series of samples. Each series of samples forms a four-layer perovskite structure in which the Co and Cr-doped samples are single-phase structures, whereas in a sample doped with Ni and Mn A small amount of oxide is present. The hysteresis loop of each series of samples presents a typical ferromagnetic "S" type. In addition to the improvement of the magnetic performance of the sample, the remaining three series of samples, in the scope of this article, are all the same as in the "x=0.3" The magnetic properties of the product are the best. The intrinsic physics of this phenomenon is studied from the concentration ratio of the different magnetic ions and the position of the magnetic ion doping. The mechanism has been discussed. For the better Fe-doped and Co-doped "x=0.3" samples at room temperature, we have carried out the characterization of the magneto-electric coupling at room temperature. When the electric field of the test is small, the external magnetic field applied synchronously with the test electric field makes both samples show the effect of the magnetic capacitance at room temperature. When the test electric field is large, the external magnetic field applied synchronously with the test electric field increases the Ni-doped sample. The value of Pr and Ec. This theory The main innovation point of the paper is as follows:1. In the three-layer perovskite ferroelectric BTO, the best magnetic modification method in this paper is found. i. e., the b-bit magnetic element is co-doped. the b-bit fe and co-magnetic co-doping, when fe: co = l: l, the sample has the best room temperature polydoping and has been observed 2. In the four-layer perovskite ferroelectric BTF magnetic doping modification of this paper, the "x=0.3" phenomenon is found, that is, when Fe: M is 7:3 (M is the incorporated magnetic ion), the magnetic modification effect of the sample is the best; in addition, in the

"x = In the 0.3 " sample, you can also
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM221

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