铽—钛酸铜钙和铌—钛酸钡陶瓷的电学性质及缺陷化学的研究

发布时间：2018-04-02 00:16

本文选题：CaCu_3Ti_4O_(12)　切入点：BaTiO_3　出处：《吉林大学》2017年硕士论文

【摘要】：CaCu_3Ti_4O_(12)(CCTO)属于ACu3Ti4O12家族,首次由Subramanian等人发现。CaCu_3Ti_4O_(12)表现出最特殊的性质,并且在1 kHz时,具有大约12000的高介电常数(e')。它的e'从室温到300°C几乎与温度无关,且在102~106 Hz范围内与频率无关。这些结果表明,CCTO陶瓷具有电容器应用的潜力。由于BaTiO_3良好的特性,其在电子陶瓷和微电子领域是一种非常有吸引力的材料。其高介电常数(e')和低介电损耗(tanδ)使钛酸钡成为许多应用的极好选择。掺杂的钛酸钡已经在半导体、正温度系数电阻(PTCR)、超声换能器、压电器件中广泛应用,并且已经成为最重要的铁电陶瓷之一。研究了烧结时间和掺杂离子的位占据对CCTO陶瓷的高e'和高tanδ的影响。研究了Nb掺杂BaTiO_3陶瓷的结构、微结构、介电、电学性质以及点缺陷。主要内容如下:1、研究不同烧结时间对CCTO的微观结构、介电和电学性质的影响。结果表明:CCTO陶瓷的介电性能受微观结构影响,随着平均晶粒尺寸的增加,e'增加。经阻抗和导纳谱研究,低频下的巨介电性质主要是受晶界电容(C_(gb))的影响,而高频下的介电平台主要受晶粒电容(C_g)的影响,并且介电弛豫进程与晶粒电阻(Rg)密切相关。随着烧结时间延长,tanδ降低,tanδ与总电阻成反比,受晶界电阻(R_(gb))控制。2、单相立方结构Ca_(1-3x/2)Tb_xCu_3Ti_4O_(12)陶瓷提高了CCTO的tanδ。这主要归功于Tb离子的掺杂修饰了CCTO的晶界的化学结构,降低了晶界的势垒高度(φ_B),使得更多的电荷载流子能通过晶界势垒,提高了tanδ。3、单相Ca_(1-3x/2)Tb_xCu_3Ti_(4-x)Tb_xO_(12)(CTCTT)陶瓷的晶粒生长受抑制,归结于溶解拖拽机制。拉曼(RS)表明CTCTT中存在多声子效应,XPS表明CTCTT中以Cu~(2+)/Cu~+,Ti~(4+)/Ti~(3+)和Tb~(3+)/Tb~(4+)混合价形式存在。Tb掺杂CCTO导致e'降低,tanδ升高。对CTCTT的缺陷化学和阻抗谱(IS)的分析证实:e'的降低和tanδ的增加主要是由于Ti位的Tb~(4+)的受主效应导致CTCTT晶粒中的导电性降低,进而影响内部阻挡层电容(IBLC)效应。4、四方结构的Ba(Ti_(1-x/4)Nb_x)O_3(x=0.03)(BTN)陶瓷以盘状晶粒和细晶粒共存。x=0.05的BTN陶瓷展示立方陶瓷、高密度(ρr=98%)、均匀的Nb富的细晶粒微结构,Nb离子以Nb~(5+)(百分比:80%)、Nb4+(~11%)和Nb~(3+)(~9%)的混合价形式存在。BTN陶瓷内存在Ba空位和Ti空位。来自Nb~(5+)的施主效应的电子补偿在BTN中占优势。x=0.05的BTN高密度陶瓷是室温电阻率ρRT=2×104Ωcm的半导体,而不是常规的电介质。
[Abstract]:CaCu3Ti4Ostit belongs to the ACu3Ti4O12 family, first discovered by Subramanian et al., which shows the most special nature, and has a high dielectric constant of about 12000 at 1 kHz. Its e'is almost independent of temperature from room temperature to 300 掳C, The results show that CCTO ceramics have the potential of capacitor application. Due to the good properties of BaTiO_3, It is a very attractive material in the field of electronic ceramics and microelectronics. Its high dielectric constant and low dielectric loss make barium titanate an excellent choice for many applications. Doped barium titanate has been used in semiconductors. Positive temperature coefficient resistor PTCRs, ultrasonic transducers, piezoelectric devices are widely used. And it has become one of the most important ferroelectric ceramics. The effects of sintering time and potential occupation of doped ions on the high e' and high tan 未 of CCTO ceramics are studied. The structure, microstructure, dielectric properties of NB doped BaTiO_3 ceramics are studied. The main contents are as follows: 1. The effects of sintering time on the microstructure, dielectric and electrical properties of CCTO are studied. The results show that the dielectric properties of CCTO ceramics are affected by the microstructure. With the increase of average grain size, the results of impedance and admittance spectra show that the giant dielectric properties at low frequency are mainly affected by grain boundary capacitance C / g / g / b), while the dielectric platform at high frequency is mainly affected by grain capacitance / C g / g. The dielectric relaxation process is closely related to the grain resistance (Rg). With the increase of sintering time, the decrease of tan 未 is inversely proportional to the total resistance. Controlled by grain boundary resistance (RSP). (2) single phase cubic CaStut 1 to 3 x / 2 Tbx / 2) Ceramics have increased the tan 未 of CCTO. This is mainly due to the addition of TB ions to modify the chemical structure of CCTO's grain boundaries. By lowering the grain boundary barrier height, more charge carriers can pass through the grain boundary potential barrier, thus increasing the tan 未 .3, single phase CaBX Cu3TiTiTiK4 TbxCu3TiTiP4 TbxOT, and the grain growth of the CTCTCTCTT ceramics is inhibited, and the results show that the grain growth of the ceramics has been inhibited by the increase in the number of charge carriers passing through the grain boundary barrier, the increase in tan 未. 3 and the increase in the grain growth of the ceramics. Raman spectroscopy (RS) indicates that there are multiphonon effects in CTCTT. It shows that there is a mixed valence in CTCTT in the form of Cu~(2 / Cu / Cu / TbDX (3) and Tb~(3 / / Tbbtn4). The existence of CCTO doping leads to the increase of e' -degrade tan 未. The defect chemistry and impedance spectroscopy of CTCTT. The decrease of tan 未 and the decrease of tan 未 are mainly due to the decrease of conductivity in CTCTT grains due to the acceptor effect of Tb~(4 at Ti position. Furthermore, the internal barrier layer capacitance (IBLC) effect .4. the tetragonal Baantitike 1-x / 4nbsp / 4 NbxSZ / 4 NbxSX / 0. 03 BTN ceramics exhibit cubic ceramics with disk-shaped and fine-grained BTN ceramics. There are Ba vacancies and Ti vacancies in BTN ceramics in the form of mixed valence in the form of Nb~(5 (percentage: 80% Nb4 + 11) and Nb~(3. The electronic compensation of donor effect from Nb~(5) is in the form of Ba vacancies and Ti vacancies in BTN ceramics. The high density BTN ceramics with advantage. X0. 05 are semiconductors with resistivity 蟻 RT=2 脳 104 惟 cm at room temperature. Instead of conventional dielectric.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1

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