CaCu3Ti4O12陶瓷的高温介电弛豫研究

研究过渡金属氧化物在交变电场中的极化和弛豫行为有助于对此类化合物的输运机制的理解和介电、铁电等性能的优化。本文利用宽温宽频介电分析仪研究了CaCu₃Ti₄O₁₂(CCTO)陶瓷在室温以上的介电常数、弛豫和阻抗等性质。通过对阻抗谱的拟合分析表明,与室温以下介电弛豫机制不同,高温弛豫激活能与晶界电导激活能完全一致,说明高温下介电弛豫源于多晶陶瓷的晶界效应。     

Dielectric Properties of Polytetrafluoroethylene/CaCu_3Ti_4O_(12) Composites

Polymer-based composite was investigated by embedding calcium copper titanate(CaCu_3Ti_4O_(12); CCTO) fillers into polytetrafluoroethylene(PTFE) matrix. The dielectric performances of the composite were investigated within the frequency range from 100 Hz to 1 MHz. It is indicated that dielectric permittivity(ε) and dielectric loss(tanδ) increase gradually as the filler content increases. Dielectric permittivity for the composite with 50 vol% CCTO filler loading is 33.5, approximately 16 times higher than that of pure PTFE(ε = 2.1) at 100 Hz. As the frequency increases, the dielectric loss decreases rapidly and reaches stability, and then remains low when the frequency rises to 1 MHz. The values for dielectric permittivity and dielectric loss in the microwave frequency(8-13 GHz) are lower than that in low frequency of 10 kHz for the composites because of different polarization modes. Several theoretical models were implemented to compare the experimental results with the theoretical calculations and the modified Lichtenecker equation was found to fit the best.     

CaCu3Ti3.95Zr0.05O12陶瓷的介电性质研究

CaCu₃Ti₄O₁₂(CCTO)陶瓷具有高介电常数,研究掺杂离子对其结构和性质的影响有助于理解并优化其介电性能。本文利用X射线衍射仪（XRD）研究了CaCu₃Ti_3.95Zr_0.05O₁₂(CCTZ)陶瓷的结构,并利用宽温宽频介电分析仪研究了其在不同温度下介电常数、弛豫、阻抗和电模量等性质。XRD结果表明,5%的Zr能够完全并入到CCTO晶格中;阻抗谱和电模量的分析表明,低温和高温范围内的介电弛豫分别与晶粒和晶界的电学性质密切相关。Zr掺杂造成晶粒激活能增大,而晶界激活能几乎不变。     

CaCu_3Ti_4O_(12)陶瓷的制备及低温介电弛豫研究

利用传统的固相反应法在不同条件下制备CaCu_3Ti_4O_(12)(CCTO)介电陶瓷,通过粉末XRD测试对其结构进行表征,以获得纯相CCTO陶瓷的合成条件.XRD结果表明,1 100℃/12 h烧结条件下制备的CCTO陶瓷结晶性好且为纯相;介电测试表明,样品在低温下存在介电弛豫,分析表明低温介电弛豫来源于晶粒的本征效应.     

固相法制备CaCu_3Ti_4O_(12)及其结构与介电性能的研究

通过固相反应合成了ABO_3型钙钛矿结构CaCu_3Ti_4O_(12)(CCTO)巨介电常数陶瓷材料.采用X射线衍射、扫描电镜和Agilent4294A精密阻抗分析仪对不同烧结温度下样品进行了物相、显微结构及其介电-频率特性的测试分析.结果表明:在温度高于950℃时,反应充分,可完全生成CCTO,1 120℃烧结温度保温6 h的CCTO介电陶瓷,致密性好、晶粒大小均匀、结晶良好,具有优良的综合介电性能.     

Dielectric Properties of Bi_4Ti_3O_(12) Ceramics by Impedance Spectroscopic Method

Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi_4Ti_3O_(12) is a type of ferroelectric ceramics, which is supposed to replace leadcontaining ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi_4Ti_3O_(12) made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi_4Ti_3O_(12) ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800 ℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50 ℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100 ℃, r values peak can reach 205.40 at a frequency of 100 k Hz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values of Ea range from 0.52 to 0.68 e V. The dielectric properties of the sample sintered at 1 100 ℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi_4Ti_3O_(12) ceramics are a kind of dielectrics. Thus, Bi_4Ti_3O_(12) can be used in high-temperature capacitors and microwave ceramics.     

(Ba_(1-y)Ce_y)(Ti_(1-x-y/4)Ce_x)O_3陶瓷的介电性能

固相反应制备(Ba_(1-y)Ce_y)(Ti_(1-x-y/4)Ce_x)O_3(y=0.03;x=0.01,0.03,0.05)陶瓷.仅在x=0.05(BCTC5)时形成具有立方结构的单相固溶体.通过XRD、SEM、RS以及介电测试研究了(Ba1-yCey)(Ti1-x-y/4Cex)O3陶瓷的结构和介电性能.BCTC5显示不均匀晶粒组成,具有立方结构,Ce掺杂后主要以Ba位Ce~(3+)和Ti位Ce~(4+)存在.两性的Ce~(3+)/Ce~(4+)能在BaTiO_3(TC=125℃)居里点引发原位扩散相变.     

高温固相法合成尖晶石型Li4Ti5O12及其性能研究

以Li₂CO₃ 和TiO₂ 为原料,以乙醇为分散剂,采用高温固相方法合成Li₄Ti₅O₁₂锂离子电池负极材 料,利用XRD、SEM 和电化学测试等方法对合成材料的结构、形貌以及电化学性能进行了表征。系统考察了热处理 温度对Li₄Ti₅O₁₂负极材料结构及电化学性能的影响,同时也研究了锂的投料量对Li₄Ti₅O₁₂电化学性能的影响。在 1.0~2.2V(vs.Li/Li ⁺ )范围内,以0.1mA/cm² 的电流密度对最佳工艺条件下合成的Li₄Ti₅O₁₂负极材料进行了恒 电流充放电测试。其首次放电比容量为167mAh/g,经过30周充放电循环后放电比容量几乎没有衰减,表现出较 大的初始放电比容量和良好的循环性能。     

Co_2O_3掺杂Ba(Ti_(0.91)Zr_(0.09))O_3陶瓷介电性能研究

采用固相反应法制备了Co2O3掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,研究了Co2O3掺杂对Ba(Ti0.91Zr0.09)O3陶瓷相结构与介电性能的影响。结果表明,掺杂Co2O3后Ba(Ti0.91Zr0.09)O3陶瓷产生了第二相,随着Co2O3施主掺杂量的增加,抑制了第二相的产生,掺杂后的Ba(Ti0.91Zr0.09)O3陶瓷是具有弥散相变的铁电体,弥散程度随掺杂量的增加而增加,x=0.01时,矫顽场最大。     

Synthesis and Dielectric Properties of Ba_3NaBiNb_(10)O_(30) Ceramics

1　ＩｎｔｒｏｄｕｃｔｉｏｎＦｅｒｒｏｅｌｅｃｔｒｉｃｓｗｉｔｈｔｈｅｔｕｎｇｓｔｅｎｂｒｏｎｚｅｔｙｐｅｓｔｒｕｃｔｕｒｅｈａｖｅｅｘｃｅｌｌｅｎｔｆｅｒｒｏｅｌｅｃｔｒｉｃ ,ｐｉｅｚｏｅｌｅｃｔｒｉｃ ,ｐｙｒｏｅｌｅｃｔｒｉｃ ,ｅｌｅｃｔｒｏ ｏｐｔｉｃ ,ａｎｄｎｏｎｌｉｎｅａｒｏｐｔｉｃａｌｐｒｏｐｅｒｔｉｅｓ[1,2 ] .Ｔｕｎｇ ｓｔｅｎｂｒｏｎｚｅｓｔｒｕｃｔｕｒｅｃｏｎｓｉｓｔｓｏｆａｎａｓｓｅｍｂｌａｇｅｏｆｃｏｒｎｅｒ ｓｈａｒｅｄ [ＭＯ6 ]ｏｃｔａｈｅｄｒａｌ (Ｍ =Ｔｉ,Ｎｂ ,Ｔａ ,ｏｒ…     

Effect of Annealing on Ferroelectric Properties of Bi_ (3.25)La_(0.75)Ti_3O_ (12) Thin Films Prepared by the Sol-gel Method

1Introduction Therehavebeenextensiveresearcheffortstoen hancethereliabilityofperovskite basedferroelectricthinfilmsforapplicationinNVFRAM(nonvolatileferroelectric randomaccessmemory)devices[1,2].Manyferroelectricmaterials,suchasPbZrxTi1-xO3(PZT),SrBi2Ti2O…     

Enhanced Ferroelectric Polarization in Laser-ablated Bi_4Ti_3O_(12) Thin Films by Controlling Preferred Orientation

Polycrystalline Bi_4Ti_3O_(12) thin films with various fractions of a-axis, c-axis and random orientations have been grown on Pt(111)/Ti/Si O_2/Si substrates by laser-ablation under different kinetic growth conditions. The relationship between the structure and ferroelectric property of the films was investigated, so as to explore the possibility of enhancing ferroelectric polarization by controlling the preferred orientation. The structural characterization indicated that the large growth rate and high oxygen background pressure were both favorable for the growth of non-c-axis oriented grains in the Bi_4Ti_3O_(12) thin films. The films with high fractions of a-axis and random orientations, i e, f(a-sxis) = 28.3% and f(random) = 69.6%, could be obtained at the deposition temperature of 973 K, oxygen partial pressure of 15 Pa and laser fluence of 4.6 J/cm~2, respectively. It was also noted that the variation of ferroelectric polarization was in accordance with the evolution non-c-axis orientation. A large value of remanent polarization(2 Pr = 35.5 μC/cm~2) was obtained for the Bi_4Ti_3O_(12) thin films with significant non-c-axis orientation, even higher than that of rare-earth-doped Bi_4Ti_3O_(12) films.     

Bi4Ti3O12陶瓷及其A和B位掺杂的介电研究

测量了Bi4Ti3O12(BTO)陶瓷及其A和B位掺杂的系列材料介电损耗。在温度损耗谱上观察到一损耗峰，通过氧处理和内耗等相关实验手段，证实该峰（PI）是与氧空位有关的弛豫峰。同时观察该峰随不同掺杂类型的变化，分析了BTO陶瓷B位掺杂对铁电性的影响。     

Synthesis and Microstructure of Partly-oriented Bismuth Layer Structure Ferroelectrics Ceramics SrBi_4Ti_4O_(15)

1IntroductionSrBi4Ti4O15is one of Aurivillius family members,whichis called the bismuth layer structure ferroelectrics(abbreviated as BLSF).The layered structure consists of(Bi2O2)2 layers interleaved with perovskite like(Am-1BmO3m 1)layers,whereAis a mon…     

Preparation, Characterization and Dielectric Properties of Ba_6Mg_(0.67)Nb_(9.33)O_(30) Ceramic

1IntroductionSince the discovery of ferroelectricity andrelated prop-ertiesin BaTiO3,alarge amount of research workonoxides,insearch of novel materials for industrial applications,hasbeen done.High performance dielectric ceramics is appliedas key material…     

Bi_4Ti_3O_(12)粉体的性能、应用及制备

介绍了钛酸铋粉体的结构、性能及应用 ,并重点介绍了钛酸铋粉体的几种主要制备方法     

(Ba_(0.94)La_(0.06))Ti_(0.985)O_3陶瓷的低温相变点的确定

为了对国产X射线衍射仪(XRD)进行低于室温的温度校正,采用冷压陶瓷技术制备了(Ba1-xLax)Ti1-x/4O3(x=0.06)(BL6T)陶瓷样品.BL6T陶瓷的铁电相变点(TC)由升温的介电温谱和降温的拉曼光谱技术确定.结果表明:BL6T具有一级相变特征,符合变温XRD校正要求.但BL6T显示热弛豫效应,采用两种技术确定的相变点分别发生在-3和-6℃,两者显示较小的热弛豫(3℃).     

Bi_(3.25)La_(0.75)Ti_3O_(12)纳米材料的水热合成研究

以分析纯硝酸铋、硝酸镧、钛酸四丁酯为原料,采用水热法制备了Bi3.25La0.75Ti3O12(BLT)纳米材料。用XRD和SEM对样品的物相和形貌进行了表征。讨论了矿化剂(NaOH)浓度和水热反应时间对BLT物相的影响。表明合成产物为正交相钙钛矿结构Bi3.25La0.75Ti3O12纳米片,厚度约10 nm,平均边缘尺寸约100 nm。当反应温度为200℃时,反应时间在12 h到48 h,矿化剂浓度在1 mol/L到2 mol/L范围内能有效合成Bi3.25La0.75Ti3O12。     

（Y—ZrO_2）－Al_2O_3陶瓷（AZ）的摩擦磨损

通过ＳＥＭ、ＴＥＭ和ＸＲＤ等手段对以Ｙ２Ｏ３为稳定剂ＺｒＯ２增韧的Ａｌ２Ｏ３陶瓷复合材料的显微结构、力学性能及与钢对摩时的摩擦磨损行为进行了系统分析，并对其微观机理做了初步探讨．结果表明，转移层的出现对对摩材料起到了保护作用；ＺｒＯ２的加入提高了材料的耐磨性能，但摩擦高温会导致ＺｒＯ２ｔ→ｍ相交增韧作用失效．     

Ferroelectric properties of Bi_4Zr_(0.5)Ti_(2.5)O_(12) thin films prepared on LaNiO_3 bottom electrode by sol-gel method

The Bi4Zr0.5Ti2.5O12 (BZT) thin films were fabricated on the LaNiO3 bottom electrode using sol-gel method. The structure and morphology of the films were character-ized using X-ray diffraction, AFM and SEM. The results show that the films have a perovskite phase and dense microstructure. The 2Pr and 2Vc of the Pt/BZT/LaNiO3 capacitor are 28.2 μC/cm2 and 14.7 V respectively at an applied voltage of 25 V. After the switching of 1×1010 cycles, the Pr value decreases to 87% of its pre-fatigue val-ues. The dielectric constant (ε) and the dissipation factor (tanδ) of the BZT thin films are about 204 and 0.029 at 1 kHz, respectively. The films show good insulating behavior according to the test of leakage current. The clockwise C-V hysteresis curve observed shows that the Pt/BZT/LaNiO3 structure has a memory effect be-cause of the BZT film’s ferroelectric polarization.