铋层状钙钛矿氧化物（n=6、7）材料中的A、B位改性研究
发布时间：2018-10-11 09:35
【摘要】：具有Aurivillius结构的含铋层状氧化物材料(Bi4Bin-3Fen-3Ti3O3n+3,n-BFTO)是一种可以在室温或室温以上同时表现出铁电性和铁磁性的单相多铁材料,在高密度存储、传感、自旋电子器件等领域有着很大的潜在应用价值。 值得注意的是,现有n-BFTO材料的铁电、铁磁性能相对较弱,并且与材料的层数有紧密的联系。为进一步提高n-BFTO的多铁性能,本文主要进行以下研究,包括：1)结构层数对B位Co部分取代Fe的BFTO材料铁磁性能的影响；2)优选了具有七层结构的BFTO,对其分别进行A位或者B位掺杂取代,以及A、B位共掺杂取代,研究对应陶瓷材料的物相结构、铁电、铁磁、介电、发光等性能；3)对A、B位共掺杂取代的具有六层结构的BFTO的铁电、铁磁、漏电等性能进行研究,并与7层结构的材料相对比,进一步讨论层数对材料多铁性能的影响。论文主要结果如下： 第一章：主要介绍了多铁材料的相关概念,BFTO材料的研究发展历史,以及BFTO陶瓷常用的制备方法和性能表征手段。 第二章：通过固定B位Co取代浓度的方式,探讨n-BFTO材料的结构层数对材料铁磁性能的影响。研究发现随着层数的增加,Fe-O-Co耦合数会增加,因而导致铁磁性能提高。此外与偶数层材料相比,奇数层材料中更有利于获得好的铁磁性。这主要是因为后者是结构对称性更低的单斜相,更有利于增强Fe-O-Co间的耦合强度从而提高铁磁性能。 第三章：研究了在B位钴掺杂的浓度对Bi8Fe4Ti3O24(7-BFTO)陶瓷结构、铁电、铁磁和介电性能的影响。发现在7-BFTO材料中,Co对Fe的最大可取代量并不是由材料的容忍因子决定(Fe和Co离子半径非常接近,从容忍因子上来讲,是可以完全互相取代的),而热力学因素的影响可能更大。要保证材料的稳定七层结构,Co和Fe的最大原子个数比为0.4:3.6,否则合成过程中材料的结构会出现坍塌并会伴随着杂相的出现。对于保持有七层稳定结构的材料,Co对Fe的取代量越多,铁磁性能越好,材料最优的铁磁性能在Co:Fe=0.4:3.6时出现,而铁电性能最优出现在Co:Fe=0.33.7处,前者主要由最大的磁性耦合离子对数目决定,而后者取决于Co取代铁对材料结构和漏电性的影响。 第四章：研究Eu和Co在A、B位共掺杂时7-BFTO陶瓷材料中的荧光、铁电和铁磁性能。我们发现在这种层状结构材料中,稀土离子发光的浓度淬灭作用可以得到一定程度上的抑制,这可能是由于BFTO材料独特的层状结构对晶胞内稀土离子相互之间距离和所处格位有着一定的调控作用。另外Eu的掺杂对材料的铁电铁磁性能也有较为明显的影响。 第五章利用贵金属的表面等离激元,来增强稀土离子掺杂的7-BFTO (BLnFTO)材料中光致发光强度。设计并制备了具有核-壳-壳结构Ag/SiO2/BLnFTO的材料。但是实验发现以Ag作为提供表面等离激元的中心不是很合适,这主要是因为Ag在样品进行热处理时,容易发生氧化并从材料中扩散消失等问题,不利于材料的性能和使用寿命。 第六章：主要研究了在La、Co共掺的Bi6-xLaxFe1.5Co1.5Ti3O21(6-BLFCT)材料中,铁磁和铁电性能随着La掺杂浓度的变化关系。发现铁磁和铁电性能在一定的La掺杂浓度范围内会随着La的增加而增大,都在x=0.75处达到最大,这是由于La掺杂对于材料晶体结构的修饰以及晶体结构对磁耦合结构的影响。之后系统研究了La掺杂对材料中主要离子的价态和导电性的影响,也发现高价离子最稳定和导电率最低时都是La:Bi=0.75:6.25。 最后第七章是全文内容的总结以及对未来工作的展望。
[Abstract]:Bi4Bin-3Fen-3Ti3O3n + 3, n-BFTO with Aurivilius structure is a single-phase polyiron material which can exhibit ferroelectricity and ferromagnetism at room temperature or at room temperature, and has great potential application value in the fields of high density storage, sensing, spin electronics and so on. Notably, the iron and ferromagnetic properties of the existing n-BFTO material are relatively weak and are closely related to the number of layers of material In order to further improve the multi-iron performance of n-BFTO, this paper mainly studies the following research, including: 1) the effect of the number of structural layers on the ferromagnetic properties of the BFTO material substituted by the B-bit Co part; 2) the BFTO with the seven-layer structure is preferred, and the A-bit or the B-bit doping are respectively carried out to replace the Fe-based BFTO material. A, B-bit co-doping is substituted to study properties such as phase structure, ferroelectric, ferromagnetic, dielectric, luminescence and other properties of the corresponding ceramic materials; 3) the properties of iron, ferromagnetic, and electric leakage of the BFTO, which are replaced by the A and B co-doping, are studied and compared with the material of the 7-layer structure. In contrast, it is further discussed that the number of layers on the multi-iron performance of the material Impact. Main results of the thesis The first chapter is as follows: Chapter 1: It mainly introduces the related concepts of multi-iron materials, the research and development history of BFTO materials, and the preparation methods and properties of BFTO ceramics. The second chapter discusses the structure and number of n-BFTO materials by fixing B-bit Co substitution concentration. The results show that the coupling number of Fe-O-Co increases with the increase of the number of layers. in addition to an even layer material, that odd layer material is more advantageous, Good ferromagnetic properties are obtained. This is mainly because the latter is a phase with lower structural symmetry and is more conducive to enhancing the coupling strength between Fe-O-Co. In the third chapter, the structure of Bi8Fe4Ti3O24 (7-BFTO) ceramic and iron were studied. In the 7-BFTO material, the maximum substitutability of Co to Fe is not determined by the tolerance factor of the material (Fe and Co ion radii are very close, from the tolerance factor, they can be completely replaced with each other), and heat The influence of mechanical factors may be greater. To ensure the stable seven-layer structure of the material, the maximum atomic number of Co and Fe is 0. 4: 3. 6. Otherwise, the structure of the material in the synthesis process will occur. In the case of Co: Fe = 0. 4: 3. 6, the better the ferroelectricity can be found in Co: Fe = 0. 33. 7, the former is the largest. the number of magnetic coupling ions is determined and the latter depends on the co-substituted iron pair, The effects of Eu and Co in A and B co-doped 7-BFTO ceramics were studied. In this layered structure, the concentration quenching of rare earth ions can be suppressed to some extent, which may be due to the unique layered structure of BFTO material and the distance between the rare earth ions in the unit cell. and the doping of the Eu is different to the iron of the material. In the fifth chapter, the 7-BFTO doped with rare earth ions is enhanced by using the surface plasmon and the like of the noble metal. Photoluminescence intensity in (BLnFTO) material, design and preparation of nuclear-shell-shell structure Ag/ SiO2/ BLnFTO materials. However, it is found that Ag is not very suitable as the center of the excitation element, such as surface, because Ag can easily oxidize and disappear from the material when the sample is subjected to heat treatment. Six-xLaxFe1. 5Co1. 5Ti3O21 (6-BLFCT) materials co-doped with La and Co were studied. The ferromagnetic and ferroelectric properties can vary with the La doping concentration. It is found that the ferromagnetic and ferroelectric properties can increase with the increase of La in a certain La doping concentration range, reaching the maximum at x = 0. 75, which is due to the La doping on the material crystal. The effect of structure modification and crystal structure on the structure of magnetic coupling is studied. The influence of La doping on valence state and conductivity of main ions in material is studied, and the most stable and conductive rate of high valence ions is also found. The minimum time is La: Bi = 0. 75: 6. 25.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB34;TM271
本文编号：2263717
[Abstract]:Bi4Bin-3Fen-3Ti3O3n + 3, n-BFTO with Aurivilius structure is a single-phase polyiron material which can exhibit ferroelectricity and ferromagnetism at room temperature or at room temperature, and has great potential application value in the fields of high density storage, sensing, spin electronics and so on. Notably, the iron and ferromagnetic properties of the existing n-BFTO material are relatively weak and are closely related to the number of layers of material In order to further improve the multi-iron performance of n-BFTO, this paper mainly studies the following research, including: 1) the effect of the number of structural layers on the ferromagnetic properties of the BFTO material substituted by the B-bit Co part; 2) the BFTO with the seven-layer structure is preferred, and the A-bit or the B-bit doping are respectively carried out to replace the Fe-based BFTO material. A, B-bit co-doping is substituted to study properties such as phase structure, ferroelectric, ferromagnetic, dielectric, luminescence and other properties of the corresponding ceramic materials; 3) the properties of iron, ferromagnetic, and electric leakage of the BFTO, which are replaced by the A and B co-doping, are studied and compared with the material of the 7-layer structure. In contrast, it is further discussed that the number of layers on the multi-iron performance of the material Impact. Main results of the thesis The first chapter is as follows: Chapter 1: It mainly introduces the related concepts of multi-iron materials, the research and development history of BFTO materials, and the preparation methods and properties of BFTO ceramics. The second chapter discusses the structure and number of n-BFTO materials by fixing B-bit Co substitution concentration. The results show that the coupling number of Fe-O-Co increases with the increase of the number of layers. in addition to an even layer material, that odd layer material is more advantageous, Good ferromagnetic properties are obtained. This is mainly because the latter is a phase with lower structural symmetry and is more conducive to enhancing the coupling strength between Fe-O-Co. In the third chapter, the structure of Bi8Fe4Ti3O24 (7-BFTO) ceramic and iron were studied. In the 7-BFTO material, the maximum substitutability of Co to Fe is not determined by the tolerance factor of the material (Fe and Co ion radii are very close, from the tolerance factor, they can be completely replaced with each other), and heat The influence of mechanical factors may be greater. To ensure the stable seven-layer structure of the material, the maximum atomic number of Co and Fe is 0. 4: 3. 6. Otherwise, the structure of the material in the synthesis process will occur. In the case of Co: Fe = 0. 4: 3. 6, the better the ferroelectricity can be found in Co: Fe = 0. 33. 7, the former is the largest. the number of magnetic coupling ions is determined and the latter depends on the co-substituted iron pair, The effects of Eu and Co in A and B co-doped 7-BFTO ceramics were studied. In this layered structure, the concentration quenching of rare earth ions can be suppressed to some extent, which may be due to the unique layered structure of BFTO material and the distance between the rare earth ions in the unit cell. and the doping of the Eu is different to the iron of the material. In the fifth chapter, the 7-BFTO doped with rare earth ions is enhanced by using the surface plasmon and the like of the noble metal. Photoluminescence intensity in (BLnFTO) material, design and preparation of nuclear-shell-shell structure Ag/ SiO2/ BLnFTO materials. However, it is found that Ag is not very suitable as the center of the excitation element, such as surface, because Ag can easily oxidize and disappear from the material when the sample is subjected to heat treatment. Six-xLaxFe1. 5Co1. 5Ti3O21 (6-BLFCT) materials co-doped with La and Co were studied. The ferromagnetic and ferroelectric properties can vary with the La doping concentration. It is found that the ferromagnetic and ferroelectric properties can increase with the increase of La in a certain La doping concentration range, reaching the maximum at x = 0. 75, which is due to the La doping on the material crystal. The effect of structure modification and crystal structure on the structure of magnetic coupling is studied. The influence of La doping on valence state and conductivity of main ions in material is studied, and the most stable and conductive rate of high valence ions is also found. The minimum time is La: Bi = 0. 75: 6. 25.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB34;TM271
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