前钙钛矿、钙钛矿相钛酸铅纳米纤维的调控生长及其复合材料研究

发布时间：2018-06-29 23:28

本文选题：前钙钛矿 + 钙钛矿　；参考：《浙江大学》2015年硕士论文

【摘要】：由于具有铁电性、压电性、高温超导特性、巨磁阻效应等丰富的物理性能,钙钛矿结构及其氧化物已广泛应用于或有望应用于铁电非挥发性存储器(FeRAM)、传感器、薄膜电容器、红外探测器、纳米发电机等。随着电子器件的多功能化及小型化,作为许多元件中重要组成部分的钙钛矿结构氧化物,其纳米尺寸调控、性能优化以及新材料的探索也日渐深入。本文首先综述了钙钛矿相氧化物的结构特点以及零维、一维和二维钙钛矿铁电氧化物纳米材料的性能及其尺寸效应研究现状；其次,对各类制备钙钛矿铁电氧化物的方法进行了对比分析；最后,简要介绍了钙钛矿结构氧化物的介电性能、铁电性能及反铁电性能。基于以上研究现状和发展趋势,本文结合改性溶胶-凝胶法、水热法和固态相变法,实现了前钙钛矿相(Pre-perovskite PbTiO3, PP-PT)及四方钙钛矿相钛酸铅(Perovskite PbTiO3, PT)纳米纤维的尺寸可控制备；将长径比高、分散性良好的PT纳米纤维与聚偏氟乙烯(PVDF)昆合制备PVDF/PP-PT复合薄膜以及PVDF/PT复合薄膜；首次采用水热法成功制备出铁电体与反铁电体复合的钛酸铅／锆酸铅(PT/PZ)复合纤维；利用高分辨透射电镜(HRTEM)、扫描电镜(SEM)、X射线衍射(XRD)、能量分散谱仪(EDS)等测试方法对所制备材料的晶体结构、微结构和元素分布进行了研究分析,揭示了调控机理及生长机制；采用多种分析测试技术对这些材料的介电性能、荧光性能等性能进行了研究。主要的研究成果如下：(1)结合改性溶胶-凝胶法和水热法,通过调节三乙醇胺(TEA)与钛酸四丁酯的比例实现了前钙钛矿相PT纳米纤维的尺寸可控制备。TEA水溶液有效地调控了Ti前驱体的溶胶-凝胶过程,使得初始反应物的分散性和均匀度都有极大的提高。进而在水热反应过程中,前钙钛矿相PT纳米纤维的成核点数量增加,抑制了纳米纤维的生长,最终合成了长度减小并且分散性良好的纳米纤维。前钙钛矿相PT纳米纤维的长度从35-90 μm减小到5-12μm,直径始终保持在100-300 nm的范围内,长径比也从225-330降低到42-60。同时,前钙钛矿相PT纳米纤维的分散性和直径均匀度得到显著提高。由于前钙钛矿相PT纳米纤维的暴露面(110)晶面为Pb-O面,Pb／Ti比值能够有效调控纳米纤维的直径。当水热反应中Pb的含量不变时,纳米纤维的直径能够保持在一定的范围内。不同尺寸前钙钛矿相PT纳米纤维的荧光发光性能研究结果表明前钙钛矿相PT纳米纤维在530-550nm处呈现出了宽的绿色发光峰,且无明显尺寸效应发生。(2)在水热过程中,以PVA和PVP作为高分子表面修饰剂,获得了长径比约为100-200且分散性良好的单晶PP-PT纳米纤维。在此基础上制备了PVDF/PP-PT复合薄膜。在频率范围为5 kHz-300 kHz,随着PP-PT纳米纤维含量的增加,PVDF/PP-PT复合薄膜的介电常数也随之增加。频率为5 kHz时,样品4(PP-PT纳米纤维加入量为20%)的介电常数(εr=9.73)比样品1(PP-PT纳米纤维加入量为O%)的介电常数(εr=6.77)高43.7%。频率高于300 kHz时,介电常数减小,介电损耗急剧增加,可能是由于PVDF以及PP-PT纳米纤维中的偶极距转向无法跟上电场的变化而发生了偶极子极化弛豫过程。同时,Cole-Cole图分析结果表明随着复合薄膜中PP-PT纳米纤维含量的增加,弛豫时间从0.4067×10-7s增加到1.2830×10-7s。(3)以单晶四方钙钛矿相PT纳米纤维为载体,与锆酸铅(PbZrO3, PZ)的前驱体进行水热反应,首次成功合成了PT/PZ单晶异质结复合纤维,长度约为15-65μm,直径约为0.70-2.05μm。界面微结构研究结果表明,单晶PT(011)晶面的晶格间距与单晶PZ(221)晶面的晶格间距相匹配,失配度为3.09%,存在外延生长的关系。PT纳米纤维与PZ晶体界面处存在约10nm的Zr、Ti元素共存区域,且Zr元素己扩散进入至PT纳米纤维内部约20 nm处,预示着PT／PZ复合纤维中较大离子半径的Zr4+离子取代了在PT纳米纤维中较小离子半径的Ti4+离子,从而使PT/PZ复合纤维中的PT纳米纤维晶胞膨胀,四方性减弱。在此基础上,提出扩散和外延生长机理来解释复合纤维的生长。(4)在PT/PZ异质结复合纤维的界面上,利用高温退火处理的方式提供Zr4+离子和Ti4+离子的互扩散动力,合成出Pb(Zr0.44Ti0.56)O3(PZT)一维材料。
[Abstract]:Due to the rich physical properties of ferroelectric, piezoelectricity, high temperature superconductivity and giant magnetoresistance, perovskite structures and their oxides have been widely used or are expected to be applied to ferroelectric nonvolatile memory (FeRAM), sensors, film capacitors, infrared detectors, nanoscale generators and so on. With the multi-function and miniaturization of electronic devices, As an important part of the perovskite structure oxide in many components, its nano size regulation, performance optimization and new materials are becoming more and more in-depth. This paper first summarizes the structure characteristics and zero dimension of perovskite phase oxides, and studies the performance and size effect of one and two dimensional Perovskite Ferroelectric oxide nanomaterials. Secondly, the methods of preparing perovskite ferroelectric oxides are compared and analyzed. At last, the dielectric properties, ferroelectric properties and antiferroelectric properties of perovskite structure oxides are briefly introduced. Based on the above research status and development trend, this paper combines the modified sol gel method, the hydrothermal method and the solid-state phase transformation method to realize the pre calcium titanium. The size of Pre-perovskite PbTiO3 (PP-PT) and tetragonal perovskite phase lead titanate (Perovskite PbTiO3, PT) nanofibers can be controlled in size, and PVDF/PP-PT composite films and PVDF/PT composite films are prepared with high length diameter ratio, good dispersive PT nanofibers and poly vinylidene fluoride (PVDF). The first preparation of iron out by hydrothermal method is the preparation of iron out for the first time. The composite fiber of lead titanate / lead zirconate (PT/PZ) composite fiber and the antiferroelectrics are used to study the crystal structure, microstructure and distribution of the material by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X ray diffraction (XRD), and energy dispersive spectrometer (EDS). The mechanism and growth mechanism of the prepared materials are revealed. The dielectric properties and fluorescence properties of these materials were studied by a variety of analysis and testing techniques. The main research results were as follows: (1) the size of.TEA water in the pre perovskite phase PT nanofibers can be controlled by adjusting the proportion of TEA and four butyl titanate with the modified sol-gel method and the hydrothermal method. The sol-gel process of Ti precursor was effectively controlled by the solution, and the dispersion and uniformity of the initial reactants were greatly improved. In the process of hydrothermal reaction, the number of nucleation points of the preperovskite PT nanofibers increased and the growth of nanofibers was inhibited. Finally, the nanofibers with reduced length and good dispersibility were synthesized. Fiber. The length of PT nanofibers in the pre perovskite phase decreases from 35-90 to 5-12 m, the diameter is kept in the range of 100-300 nm, the length to diameter ratio is also reduced from 225-330 to 42-60.. The dispersion and diameter uniformity of the pre perovskite PT nanofibers are significantly improved. Due to the riot surface (110) surface (110) of the pre perovskite phase PT nanofibers The diameter of nanofibers can be effectively regulated by the ratio of Pb / Ti to the Pb-O surface. When the content of Pb is constant in the hydrothermal reaction, the diameter of the nanofibers can be kept in a certain range. The fluorescence luminescence properties of the perovskite PT nanofibers before different sizes show that the pre perovskite PT nanofibers are wide in the 530-550nm width. The green luminescence peak has no obvious size effect. (2) in the hydrothermal process, PVA and PVP are used as polymer surface modifiers to obtain the single crystal PP-PT nanofibers with a long diameter ratio of about 100-200 and good dispersion. On this basis, the PVDF/PP-PT composite thin films are prepared. The frequency range is 5 kHz-300 kHz, with the content of PP-PT nanofibers. The dielectric constant of PVDF/PP-PT composite film increases. When the frequency is 5 kHz, the dielectric constant (epsilon r=9.73) of sample 4 (PP-PT nanofiber adding 20%) is higher than that of sample 1 (PP-PT nanofiber O%) with high 43.7%. frequency higher than 300 kHz, and dielectric constant decreases and dielectric loss increases dramatically. The dipole polarization relaxation process has occurred because the dipole distance in PVDF and PP-PT nanofibers can not keep up with the change of the electric field. At the same time, the Cole-Cole diagram analysis shows that the relaxation time increases from 0.4067 x 10-7s to 1.2830 x 10-7s. (3) with the increase of the PP-PT nanofiber content in the composite film, and the single crystal tetragonal perovskite phase PT Nanofibers are used to react with the precursor of lead zirconate (PbZrO3, PZ). The PT/PZ single crystal heterojunction composite fiber is successfully synthesized for the first time. The length is about 15-65 u m and the diameter is about 0.70-2.05 mu m. interface microstructures. The results show that the lattice spacing of the single crystal PT (011) crystal is matched with the lattice spacing of the single crystal PZ (221) crystal surface. The degree is 3.09%, the relationship between the epitaxial growth and the relationship between.PT nanofibers and PZ crystals exists about 10nm Zr, the Ti element coexists in the region, and the Zr element has spread to about 20 nm within the PT nanofibers, indicating that the Zr4+ ion of the larger ionic radius in the PT / PZ composite fiber has replaced the smaller ion radius in the PT nanofibers. On this basis, the diffusion and epitaxial growth mechanism is proposed to explain the growth of the composite fibers. (4) the interaction between Zr4+ ions and Ti4+ ions is provided by high temperature annealing at the interface of PT/PZ heterojunction composite fibers, and Pb (Zr0.44) is synthesized. Ti0.56) O3 (PZT) one dimensional material.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ343;TB33

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