分子基铁电单晶的制备及性能调控

发布时间：2018-03-10 12:36

本文选题：分子基铁电体　切入点：铁电动力学　出处：《华东师范大学》2017年博士论文　论文类型：学位论文

【摘要】：铁电体是一类具有自发极化并且极化方向可以随外电场发生反转的固体(晶体或聚合物)或液晶材料,在电子领域具有重要的应用,如电容器、非易失性存储器、场效应晶体管、传感器、电容器等。自从1920年第一个铁电体罗息盐问世以来,铁电材料的发展和应用主要集中在无机铁电体和少数有机聚合物铁电体。现代电子学发展的趋势之一是制备纯有机电子器件,因此有机铁电体成为近年来铁电材料的研究热点,它们的发展不仅给材料化学带来了新的挑战,同时由于它们的轻便、柔韧和无毒等优点,也为铁电体在有机电子领域的应用提供了新的思路。随着研究的大量开展,几种性能良好的小分子铁电体陆续被发现,打破了人们对小分子铁电材料居里温度低、自发极化小的传统认识,为其实际应用提供了可能。此外,当铁电性与光学、磁性等性质结合时,自发电极化成为操控物质光学、磁性的新途径,同时也使得利用光和磁场来调控其自发极化成为可能。此类多功能材料,如荧光铁电材料、磁电耦合材料等,无论在基础研究方面,还是在光电器件、自旋电子学、磁电传感等应用方面都有着重要的研究意义。本文从系统研究二异丙胺盐类分子基铁电晶体的铁电特性、制备金属有机配合物单晶、磁性元素掺杂分子基铁电晶体三个方面入手,在分子基铁电单晶的制备及性能调控方面取得了以下研究成果:1.研究了溶液法直接制备二异丙胺溴(DIPAB)铁电单晶的条件,结果表明影响DIPAB晶型的关键因素是晶体生长过程中溶剂/环境中的水分:在无水条件下重结晶得到铁电相的晶体,而在含水条件下得到顺电相的晶体。在此基础上,通过热蒸发法在不同衬底上成功制备了均匀的DIPAB薄膜。2.首次对小分子铁电体DIPAB晶体的电滞回线动力学进行了研究,发现电滞回线面积A随频率f具有三个阶段的变化,不同于无机材料中常见的单峰曲线变化,结合DIPAB的结构特点,认为这可能是由于晶体中同时存在有序-无序振动和离子位移型铁电起源。通过数据拟合,得到了三个阶段A与f和电场E0之间的指数关系式。3.制备了六种不同阴离子(HF2-,Cl-,Br-,I-,NO3-,ClO4-)的二异丙胺(DIPA+)盐晶体并研究了阴离子对晶体的相变温度和铁电性能的影响,结果表明这些晶体的铁电性与阴离子的电负性和结构密切相关:对于卤素阴离子来说,电负性越大,晶体相变温度越高,极化强度越大;DIPA-C104不符合此规律是由于其相变源于C104-离子而不是DIPA+阳离子的有序-无序振动。密度泛函理论计算结果与实验结果符合。4.制备了有机-无机杂化DIPA2MnBr4单晶,晶体在420 K附近发生结构相变,电滞回线和PFM测试表明DIPA2MnBr4具有室温铁电性。此外,DIPA2MnBr4晶体在紫外灯下发强绿色荧光,量子产率高达62%,并且对醇类气体具有灵敏的荧光响应和良好的可重复性。5.以锰(Ⅱ)为金属中心,分别制备了一系列含不同有机胺配体的胺-锰(Ⅱ)-氯配合物和含不同卤素离子的吡咯烷-锰(Ⅱ)-卤素配合物的单晶,研究了有机配体和卤素离子对配合物结构和磁性、荧光等性质的影响。结果表明有机配体和卤素离子均能调控配合物的结构及性质。6.研究了巴豆酸单晶、巴豆酸钴(II)和巴豆酸锰(Ⅱ)配合物晶体的结构和性质。随后,借鉴无机半导体掺杂的概念,制备了(1:10)、(1:5)的锰(Ⅱ)和钴(Ⅱ)掺杂巴豆酸的晶体,所得到的掺杂晶体同时具有磁性和近室温铁电性,在外磁场作用下,锰(Ⅱ)掺杂巴豆酸(1:5)晶体的介电常数随温度发生明显的突变,并且突变随磁场强度增加而向高温移动,表明晶体内可能存在磁电耦合。
[Abstract]:Ferroelectrics is a kind of solid and spontaneous polarization polarization direction can be reversed with the external electric field occurs (crystal or polymer) or liquid crystal materials have important applications in the field of electronics, such as capacitors, nonvolatile memory, field effect transistors, sensors, capacitors and so on. Since 1920 the first ferroelectric Luo the advent of the development and application of salt making, ferroelectric materials mainly focused on inorganic organic polymer ferroelectrics and ferroelectrics. One of the few modern electronics is the development trend of preparation of pure organic electronic devices, so organic ferroelectric ferroelectric materials has become a hot research topic in recent years, their development is not only to material chemistry has brought new challenges, at the same time because of their lightweight, flexible and non-toxic, but also provides a new way for the application of ferroelectrics in the field of organic electronics. With the research carried out a lot, some good performance Small molecular ferroelectrics have been discovered, people broke the Curie temperature of small molecule of ferroelectric materials is low, the traditional understanding of small spontaneous polarization, provides a possibility for the practical application. In addition, when the combination of ferroelectric and optical, magnetic properties, self generating polarization is the new way to manipulate matter optical, magnetic, and at the same time makes use of optical and magnetic field to control the spontaneous polarization becomes possible. This kind of multifunctional materials, such as fluorescent ferroelectric materials, magnetoelectric materials, both in terms of basic research, or in optoelectronic devices, spintronics, has important significance on magnetoelectric and other applications. The ferroelectric properties of system two isopropylamine salt molecules based ferroelectric crystals, preparation of metal organic complexes of single crystal, the three aspects of molecular based magnetic elements doped ferroelectric crystal with in molecule based ferroelectric single crystal preparation and property control The following results are obtained: 1. the study of the solution method to directly prepare two isopropyl amine bromide (DIPAB) ferroelectric single crystal conditions, results show that the key factors affecting the DIPAB crystal is water / solvent in the process of crystal growth in the environment: under anhydrous conditions obtained by recrystallization of ferroelectric crystals in aqueous conditions get the paraelectric crystal. On this basis, through thermal evaporation on different substrates of DIPAB thin films were prepared for the first time on the.2. uniform small molecule ferroelectric crystal DIPAB hysteresis kinetics were studied, found that changes in the hysteresis loop area A with frequency f has three stages, the single peak curve of different in the inorganic material in common, combined with the structural characteristics of DIPAB, that this may be due to order-disorder vibration and displacement of ion type ferroelectric crystals exist in the origin at the same time. By fitting the data obtained three stages with F and A Six different kinds of anions prepared the exponential relationship between the.3. field E0 (HF2-, Cl-, Br-, I-, NO3-, ClO4-) two isopropylamine (DIPA+) and to study the effect of salt crystal anion on the crystal phase transition temperature and ferroelectric properties, results show that the ferroelectric properties of these crystals is closely related with the anion electronegativity and structure for halogen anion, the larger the electronegativity, the phase transition temperature is higher, the greater the intensity of polarization; DIPA-C104 does not comply with this rule is because the phase transformation from C104- ion instead of DIPA+ cation order disorder vibration. The density functional theory calculation results accord with the experimental results of organic inorganic hybrid DIPA2MnBr4 single crystal was prepared by.4., the crystal phase transition occurs near 420 K, hysteresis loop and PFM test shows that DIPA2MnBr4 has room temperature ferroelectricity. In addition, DIPA2MnBr4 crystal strong green fluorescence under UV light, quantum yield up to 62 %, and has the alcohols gas sensitive fluorescence response and good repeatability of.5. with manganese (II) metal center, were prepared by a series of different organic amine ligands containing amine - manganese (II) - chloride complexes containing different halide ions and pyrrolidine - manganese (II) - halogen study on complexes of single crystal, organic ligands and halogen ions on the structure and magnetic properties of complexes, effects of fluorescent properties. The results show that organic ligands and halogen ions can crotonic acid crystal study on regulation of.6. structure and properties of complexes of cobalt (II), crotonic acid and crotonic acid manganese (II) structure and properties the crystal structure of the complexes. Then, based on the concept of inorganic semiconductor doping, preparation of (1:10) (1:5), Mn (II) and cobalt (II) doped crotonic acid crystals doped crystals obtained with magnetic and ferroelectric properties near room temperature, the external magnetic field under the action of manganese (II crotonic acid (1:5) doped) crystal The dielectric constant abruptly changes with the temperature, and the mutation moves to the high temperature with the increase of the magnetic field intensity. It indicates that there may be a magnetoelectric coupling in the crystal.

【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM221

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