Synthesis and ionic conductivity of new layered perovskite compound, Ag2La2Ti3O10

A new layered perovskite compound, Ag₂La₂Ti₃O₁₀, was synthesized by an ion-exchange reaction of M₂La₂Ti₃O₁₀ (M = Na,K) with a AgNO₃ molten salt. The crystal structure and the ionic conductivity of the ion-exchanged compound were investigated. The ionic conductivities attributed to the interlayer silver ions were observed at high temperatures. The ionic conductivity of Ag₂La₂Ti₃O₁₀ was much higher than that of Na₂La₂Ti₃O₁₀, while the interlayer sodium ions in Na₂La₂Ti₃O₁₀ and silver ions in Ag₂La₂Ti₃O₁₀ have almost the same rock-salt type coordination. The higher conductivity of Ag₂La₂Ti₃O₁₀ is probably due to the higher polarizability of silver ions.     

Dielectric and AC conductivity behavior of BaBi2Nb2O9 ceramics

The complex dielectric and AC conductivity response of BaBi₂Nb₂O₉ relaxor ferroelectric ceramics were studied as a function of frequency (100 Hz-10 MHz) at various temperatures. The observed dielectric behavior was characterized by two types of relaxation processes which were described by the ‘universal relaxation law’. The frequency dependence of conductivity which showed a classical relaxor behavior followed the Jonscher's universal law σ(ω)=σ₀+Aωⁿ. The exponent n exhibited a minimum in the vicinity of temperatures of dielectric anomaly while the pre-factor A showed a maximum. The temperature dependence of n followed the Vogel-Fulcher relation with activation energy of about 0.14 eV.     

Influence of Lu2O3 on electrical and microstructural properties of CaCu3Ti4O12 ceramics

In this work, the influence of Lu₂O₃ doped on the dielectric and electrical properties of CaCu₃Ti₄O₁₂ was reported. Lu₂O₃-doped CCTO was prepared by a conventional solid state technique using CuO, TiO₂, and CaCO₃ as starting materials. The samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM); dielectric measurements were measured in the 10² Hz–10⁷ Hz frequency range at room temperature; and the nonlinear behavior of all samples was measured. The doping of Lu₂O₃ resulted in an increase in the dielectric constant of CCTO, but decreased the stability of the frequency dependence. Increasing concentrations of Lu₂O₃ resulted in decreasing nonlinear coefficients.     

CaCu3Ti4O12陶瓷的微观结构和电学性能

利用传统的固相反应工艺，在不同的烧结温度下制备了一系列的CaCu₃Ti₄O₁₂陶瓷样品，考察了其微观结构以及介电和复阻抗方面的电学性质.研究发现这些样品在微观结构方面可分为三种类型，高介电性与微观结构有着密切的关联性.室温下，样品的低频介电常数随陶瓷晶粒尺寸的增大而提高.随着测试温度的升高，不同微观结构类型的样品呈现出不同的电学性质的变化，但其中也存在着一些相同的特征.高温下，介电频谱呈现出一个低频介电响应和两个类Debye型弛豫色散，复阻抗谱呈现出三个Cole-Cole半圆弧.将实验上观测到的电学性质的起因归于陶瓷多晶微结构中的晶畴、晶界和晶粒内的缺陷. 关键词： 3Ti₄O₁₂')" href="#">CaCu₃Ti₄O₁₂ 微观结构 电学性质     

脉冲形成线用CaO-TiO2-Al2O3基介质陶瓷介电性能

设计了一种脉冲形成线用新型CaO-TiO2-Al2O3基介质陶瓷体系,采用传统固相法通过优化组分和制备工艺,调控材料的微结构,获得了介电性能优异的介质陶瓷。其介电常数在15~35之间可调,介电损耗小于0.002,频率稳定性好。在厚度为1 mm时,介电强度高达50 kV/mm。研究了厚度对CaO-TiO2-Al2O3基介质陶瓷介电强度的影响规律,当厚度从1 mm减小到0.1 mm时,介电强度呈非线性增大,从50 kV/mm（1 mm厚样品）提高到92 kV/mm（0.1 mm厚样品）,可见,CaO-TiO2-Al2O3基介质陶瓷的电击穿与其机械损坏具有相似性。结合CaO-TiO2-Al2O3基介质陶瓷的化学组分和微观结构,CaO-TiO2-Al2O3基介质陶瓷优越的电击穿特性可以用弱点击穿理论解释。     

Dielectric relaxation in complex perovskite oxide BaCo1/2W1/2O3

Polycrystalline BaCo_1/2W_1/2O₃ (BCW) is prepared by the solid-state reaction technique. The X-ray diffraction study of the compound at room temperature reveals the monoclinic phase. The field dependence of the dielectric constant and the conductivity are measured in the frequency range from 50 Hz to1 MHz and in the temperature range from 300 to 413 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency is performed. The frequency-dependent maxima in the imaginary impedance are found to obey an Arrhenius law with an activation energy=0.86 eV. The frequency-dependent electrical data are also analysed in the framework of the conductivity and modulus formalisms.     

钛酸铋钡陶瓷的介电性、铁电性及对晶格结构的依赖性

采用溶胶-凝胶工艺成功制备出BaBi₄Ti₄O₁₅微细粉料，并利用此微粉烧结出成瓷良好的BaBi₄Ti₄O₁₅陶瓷.研究了BaBi₄Ti₄O₁₅陶瓷的铁电 顺电相 变，测定了BaBi₄Ti₄O₁₅的介 电特性和饱和状态下的铁电特性.所作测量表明B 关键词： 铁电性 介电性 晶格结构 溶胶 凝胶法     

Dielectric properties and temperature stability of BaTiO3 co-doped La2O3 and Tm2O3

The influence of La₂O₃ and Tm₂O₃ co-doping on the dielectric properties and the temperature stability of BaTiO₃ was investigated. BaTiO₃ ceramics were prepared with the compositional formula of (Ba_1−xLa_x)(Ti_1-x/4−yTm_y)O₃. La₂O₃ and Tm₂O₃ co-doping in BaTiO₃ mainly had effects on an increase in the dielectric constant and the temperature stability, respectively. The increase of La₂O₃ concentration and the decrease of Tm₂O₃ concentration in BaTiO₃ resulted in a decrease of lattice parameter and tetragonality because La³⁺ ion substituting for Ba site is smaller than Ba²⁺ ion and Tm³⁺ ion substituting for Ti site is larger than Ti⁴⁺ ion. With the increase of La₂O₃ and the decrease of Tm₂O₃, the dielectric constant of BaTiO₃ was enhanced in spite of the reduction of tetragonality. P-E hysteresis measurements revealed that this phenomenon was based on the improvement of remanent polarization with the increase of La₂O₃ concentration. The introduction of excess Tm₂O₃ in BaTiO₃ suppressed the grain growth and BaTiO₃ ceramics showed higher temperature stability due to the stable tetragonal structure and the small grain size with the increase of Tm₂O₃ concentration.     

Dielectric properties of lanthanum-doped CaCu3Ti4O12 synthesized by semi-wet route

Effect of La³⁺ doping at Ca²⁺ site in CaCu₃Ti₄O₁₂ has been examined. Compositions with x=0.10, 0.20 and 0.30 were synthesized in the system Ca_(1−3x/2)La_xCu₃Ti₄O₁₂ by semi-wet method. Powder X-ray diffraction confirmed the formation of monophasic compounds. The structure remains cubic similar to CaCu₃Ti₄O₁₂. Lattice parameter increases slightly with increasing La³⁺ concentration. Microstructure has been studied using scanning electron microscopy (SEM). Average grain size is in the range 2-4 μm for various compositions. Energy-dispersive spectrometer (EDS) studies confirm the stoichiometry of the synthesized materials. Dielectric constant, dielectric loss and conductivity of the samples decrease with increasing lanthanum concentrations.     

Ferroelectric and dielectric properties of La/Mn co-doped Bi4Ti3O12 ceramics

La/Mn co-doped Bi4Ti3O12 ceramics,Bi3.25La0.75Ti3-xMnxO12(x=0.02,0.04,0.06,0.08),were prepared by the solid-state reaction method.The influence of manganese substitution for the titanium part in Bi 3.25 La 0.75 Ti 3 O 12 on the sintering behaviour,microstructure,Raman spectra and electrical properties was investigated.The experimental results show that the phase composition of all samples with and without manganese doping,sintered at 1000 ℃,consists of a single phase with a bismuth-layered structure belonging to the crystalline phase Bi4Ti3O12.There is no evidence of any impurity phase,but a small change in crystallographic orientation is observed.The Curie temperature of Bi3.25La0.75Ti3-xMnxO12 ceramics is steadily shifted to lower temperature with increasing Mn-doping content.Moreover,the remnant polarisation(Pr) of Bi3.25La0.75Ti2.92Mn0.08O12 samples increases with Mn-doping content,and the Bi3.25La0.75Ti2.92Mn0.08O12 sample exhibits the largest P r of 16.6 μC/cm 2.     

添加Nb对CaCu3Ti4O12陶瓷介电性能的影响

采用固相反应法制备了CaCu₃Ti_4-xNb_xO₁₂(x=0，0.01，0.04，0.08，0.2)陶瓷，样品在x取值范围内形成了连续固溶体.在40Hz—110MHz频率范围对样品进行了介电频谱分析，实验结果表明，与纯CaCu₃Ti₄O₁₂不同，含Nb试样除了在频率大于10kHz范围内出现的德拜弛豫 关键词： 巨介电常数 德拜弛豫 阻挡层电容 等效电路     

The doping effects of BiFe1-xCoxO3 (x=0.0-0.8) in layered perovskite Bi4Ti3O12 ceramics

Bi5Fe1-xCoxTi3O15(x = 0.0, 0.2, 0.4, 0.5, 0.6, and 0.8) multiferroic ceramics are synthesized in two steps using the solid state reaction technique. X-ray diffraction patterns show that the samples have four-layer Aurivillius phases. At room temperature (RT), the samples each present a remarkable coexistence of ferromagnetism (FM) and ferroelectricity (FE). The remnant polarization (2P r ) reaches its greatest value of 14 μC/cm 2 at x = 0.6. Remnant magnetization (2M r ) first increases and then decreases, and the greatest 2M r is 7.8 menu/g when x = 0.5. The magnetic properties for x = 0.4 are similar to those for x = 0.6, indicating that the magnetic properties originate mainly from the coupling between Fe 3+ and Co 3+ ions, rather than from their own magnetic moments.     

Reduced dielectric loss and leakage current in CaCu3Ti4O12/SiO2/CaCu3Ti4O12 multilayered films

The CaCu₃Ti₄O₁₂/SiO₂/CaCu₃Ti₄O₁₂ (CCTO/SiO₂/CCTO) multilayered films were prepared on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition method. It has been demonstrated that the dielectric loss and the leakage current density were significantly reduced with the increase of the SiO₂ layer thickness, accompanied with a decrease of the dielectric constant. The CCTO film with a 20 nm SiO₂ layer showed a dielectric loss of 0.065 at 100 kHz and the leakage current density of 6×10⁻⁷ A/cm² at 100 kV/cm, which were much lower than those of the single layer CCTO films. The improvement of the electric properties is ascribed to two reasons: one is the improved crystallinity; the other is the reduced free carriers in the multilayered films.     

CaCu3Ti4O12 陶瓷介电模量响应特性的研究

由于CaCu₃Ti₄O₁₂巨介电常数陶瓷的低频区直流电导较大, 本文采用模量 M"-f频谱表征与分析了低频和高频的两个松弛极化过程. 研究认为, 这两个特征峰属于晶界区Schottky 势垒耗尽层边缘深陷阱的电子松弛过程, 其中高频松弛峰起源于晶粒本征缺陷的电子松弛过程, 而低频松弛峰则为与氧空位有关的松弛极化过程. 对于CaCu₃Ti₄O₁₂这类低频下具有高直流电导的陶瓷材料, 采用模量频谱能更有效地分析研究其损耗极化机理. 关键词： 3Ti₄O₁₂陶瓷')" href="#">CaCu₃Ti₄O₁₂陶瓷 模量 松弛过程 电导     

Fe掺杂CaCu3Ti4O12陶瓷的介电性能与弛豫特性研究

采用固相反应法制备了CaCu₃Ti_4-xFe_xO₁₂(0≤x≤0.2)陶瓷,通过X射线衍射、扫描电子显微镜、介电频谱和阻抗谱等手段研究了Fe对CaCu₃Ti₄O₁₂陶瓷的结构和介电性能的影响.研究发现：CaCu₃Ti_4-xFe_{x关键词： 巨介电常数 双阻挡层电容模型 界面极化}     

Effect of Cu-stoichiometry on the dielectric and electric properties in CaCu3Ti4O12 ceramics

CaCu_3+yTi₄O₁₂ (y=0, ±0.025, ±0.05, ±0.1 and −0.15) ceramics are prepared by the conventional solid-state reaction technique under sintering condition of 1050 ^°C, 10 h. X-ray diffraction shows that they all have the good crystalline structure. Cu-deficient ceramics exhibit the microstructures of uniform grain size distribution, whereas both Cu-stoichiometric and Cu-rich ceramics display microstructures of bimodal grain size distribution. The largeness of low-frequency dielectric permittivity at room temperature is found to be very sensitive to the Cu-stoichiometry. Upon raising the measuring temperature, all of the ceramics present commonly three semicircles in the complex impedance plane. It indicates that there exist three distinct contributions, which are ascribed to arising from domains, grain boundaries and domain boundaries. In addition, the influence of CuO segregation on the dielectric and electrical properties is also discussed.     

Oxygen-defects-related dielectric response in CaCu3Ti4O12 ceramics

A 10 mm thickness columned CaCu₃Ti₄O₁₂ ceramic was fabricated by the conventional solid-state reaction method and the dielectric properties of different parts in ceramic had been investigated. For the sample close to the surface, only one Debye-type relaxation around 10⁷ Hz was observed at room temperature. However, for the sample close to the core, another relaxation peak was observed at about 10⁴ Hz. The results were explained in terms of the equivalent circuit model by showing in the impedance spectroscopy. Moreover, it was introduced that the low-frequency dielectric relaxation is associated with the electrode-sample contact effect based on varying sample thickness and an annealing treatment in the nitrogen atmospheres.     

Mo掺杂SrBi4Ti4O15陶瓷的铁电介电性能

用传统的固相烧结工艺，制备了钼掺杂铁电陶瓷样品SrBi₄Ti₄O₁₅(SBTi)铁电陶瓷SrBi_4-2x/3Ti_4-xMo_xO₁₅(x=0.00，0.003，0.012，0.03，0.06，0.09).X射线衍射的结果表明，样品均为单一的层状钙钛矿结构相，Mo掺杂未改变SBTi的晶体结构.通过扫描电子显微镜观测发现，样品晶粒为片状，随掺杂量的增加，晶粒逐 关键词： 4Ti₄O₁₅')" href="#">SrBi₄Ti₄O₁₅ Mo掺杂 剩余极化 居里温度     

Electrical properties of neodymium doped CaBi4Ti4O15 ceramics

Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi_4−xNd_xTi₄O₁₅ (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd³⁺ dopant. The effects of Nd³⁺ doping on the dielectric and ferroelectric properties of CaBi₄Ti₄O₁₅ ceramics are studied. Nd³⁺ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd³⁺ doped CaBi₄Ti₄O₁₅ ceramics was increased by 80% at x=0.25, while more Nd³⁺ dopant decreased the remnant polarization. CaBi_3.75Nd_0.25Ti₄O₁₅ ceramics had the largest piezoelectric constant d₃₃. The structure and properties of CaBi_4−xNd_xTi₄O₁₅ ceramics showed that Nd³⁺ may occupy different crystal locations when Nd³⁺ content x is less than 0.25 and more than 0.50.     

直流老化对CaCu3Ti4O12陶瓷介电性能的影响

在电场为3.5 kV/cm的条件下, 对CaCu₃Ti₄O₁₂陶瓷进行了60 h的直流老化, 研究了老化过程对CaCu₃Ti₄O₁₂陶瓷介电性能和电气特性的影响. J-E特性测试结果表明, 直流老化导致CaCu₃Ti₄O₁₂陶瓷击穿场强、非线性系数和势垒高度明显降低. 介电性能测试结果表明, 低频介电常数和介电损耗明显增大, 并且介电损耗随频率的变化遵从Debye弛豫理论, 可分解为直流电导损耗和弛豫损耗, 直流老化主要导致了电导损耗的增加. 在低温233 K, 介电损耗谱中出现两个弛豫峰, 其活化能分别为0.10, 0.50 eV, 认为对应着晶粒和畴界的弛豫过程, 且不随直流老化而变化. 通过电模量谱对CaCu₃Ti₄O₁₂陶瓷的弛豫过程进行了表征, 发现直流老化导致的界面空间电荷在外施交变电场的作用下符合Maxwell-Wagner极化效应, 并在低频区形成新的弛豫峰. 在高温323-473 K的阻抗谱中, 晶界弛豫峰在直流老化后明显向高频移动, 其对应的活化能从1.23 eV 下降到0.72 eV, 晶界阻抗值下降了约两个数量级. 最后, 建立了CaCu₃Ti₄O₁₂陶瓷的阻容电路模型, 分析了介电弛豫过程与电性能之间的关联.