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CaCu3Ti4O12介电损耗较大且损耗机理尚不明确, 因此限制了其应用.本文采用固相法和共沉淀法合成CaCu3Ti4O12陶瓷, 利用宽带介电温谱研究在交流小信号作用下, 双Schottky势垒耗尽层边缘深陷阱的电子松弛过程、 载流子松弛过程以及CaCu3Ti4O12陶瓷的介电损耗性能. 研究发现, 在低频下以跳跃电导和直流电导的响应为主, 而高频下主要为深陷阱能级的松弛过程所致, 特别是活化能为0.12 eV的深陷阱浓度, 这是决定CaCu3Ti4O12陶瓷高频区介电损耗的重要因素.降低直流电导, 有利于降低低频区介电损耗; 而高频区介电损耗的降低, 需要降低深陷阱浓度或增大晶粒尺寸. 共沉淀法制备的CaCu3Ti4O12陶瓷, 有效降低直流电导及控制深陷阱浓度, 介电损耗降低明显.
关键词:
3Ti4O12陶瓷')" href="#">CaCu3Ti4O12陶瓷
介电损耗
松弛过程
Schottky势垒 相似文献
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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 相似文献
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采用固相烧结法合成了单相巨介电常数氧化物CaCu3Ti4O12(CCTO).用阻抗分析仪分析了10—420 K温度范围内的介电频谱和阻抗谱特性,并结合ZVIEW软件进行了模拟.结果表明:温度高于室温时,频谱出现两个明显的弛豫台阶,低频弛豫介电常数随温度升高而显著增大,表现出热离子极化特点;温度低于室温时,频谱表现出类德拜弛豫,且高、低平台介电常数值基本不随温度变化,表现出界面极化特点和较好的温度稳定性.频谱中依次出现的介电弛豫对应于阻抗谱中
关键词:
3Ti4O12')" href="#">CaCu3Ti4O12
介电频谱
阻抗谱
Cole-Cole半圆弧 相似文献
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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. 相似文献
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采用传统固相反应法制备了CaCu3Ti4O12陶瓷.XRD证实其CaCu3Ti4O12相;SEM观察到明显的晶粒晶界结构,晶界区亦由小晶粒构成;结合EDS结果,判定晶界区小晶粒为CuO.在较宽的温度范围内,CaCu3Ti4O12陶瓷的介电常数保持在105左右;当频率为103 Hz温度小于150 K时,介电常数迅速下降.在173—373 K温度范围内,通过其I-V特性,得到CaCu3Ti4O12陶瓷直流电导随温度的变化:直流电导与温度的关系可分为三部分,对应的活化能分别为0.681 eV,0.155 eV和0.009 eV,这与CuO陶瓷直流电导活化能一致.可以认为晶界区的CuO小晶粒在CaCu3Ti4O12陶瓷的直流电导中占主导,这为解释CaCu3Ti4O12陶瓷反常的介电性能提供了新的思路.
关键词:
3Ti4O12')" href="#">CaCu3Ti4O12
微观结构
直流电导
介电特性 相似文献
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具有巨介电常数的CaCu3Ti4O12陶瓷是一种理想的高储能密度电容器材料.本文以草酸为沉淀剂、以乙酸铵为调节pH值的定量缓冲剂,获得制备CaCu3Ti4O12陶瓷的简化共沉淀法.确定了pH=30为制备前驱粉料的最佳反应条件.通过显微分析和介电性能测量,发现在1040℃—1100℃范围内,随着烧结温度的提高,陶瓷的品粒尺寸增大,非线性系数上升,电位梯度和介电损耗下降,1100℃烧结的试样tanδ最低达到0.04.认为CaCu3Ti4O12陶瓷介电损耗包含直流电导分量、低频松弛损耗和高频松弛损耗.低频松弛活化能为0.51 eV.,对应于晶界处的Maxwell-Wagner松弛极化;高频松弛过程活化能为0.10 eV,对应晶粒内部的氧空位缺陷.烧结温度的升高导致晶界电阻下降. 相似文献
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B. Shri Prakash 《Journal of Physics and Chemistry of Solids》2007,68(4):490-502
Detailed investigations into the dielectric dispersion phenomenon in the giant dielectric constant material CaCu3Ti4O12 (CCTO) around room temperature revealed the existence of two successive dielectric relaxations. In the temperature domain, a new dielectric relaxation was clearly observed around 250 K, in addition to the well-investigated dielectric relaxation close to 100 K. The effect of sintering and doping (La3+) on the strength of these dielectric relaxations were studied in detail. The sintering temperature as well as its duration was found to have tremendous influence on the dielectric relaxation that was encountered around 250 K. This Maxwell-Wagner (M-W) type of relaxation was found to be originating from the surface layer containing the Cu-rich phase, which was ascribed to the difference in the oxygen content between the surface and the interior of the sample. Interestingly, this particular additional relaxation was not observed in La2/3Cu3Ti4O12, a low dielectric constant member of the CCTO family, in which the segregation of Cu-rich phase on the surface was absent. Indeed the correlation between the new relaxation and the presence of Cu-rich phase in CCTO ceramics was further corroborated by the absence of the same after removing the top and bottom layers. 相似文献
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Although CdCu3Ti4O12 is isostructural to CaCu3Ti4O12, the room temperature low-frequency dielectric constant of the former compound was reported to be ∼400, only 1/25 of that of the latter material [M.A. Subramanian, et al., J. Solid State Chem. 151 (2000) 323]. In this communication, we report that the dielectric constant of CdCu3Ti4O12 can be remarkably increased by elevating the sintering temperature. The room temperature dielectric constant at 100 kHz achieves 9000, almost as much as that of CaCu3Ti4O12, for the sample sintered at 1283 K. The appearance of giant dielectric constant in CdCu3Ti4O12 is explained in terms of internal barrier layer capacitance (IBLC) effect with the subgrain boundary as the barrier. Our result supplies an approach in searching for new giant-dielectric-constant materials in the CaCu3Ti4O12 family. 相似文献
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K. Chen 《Solid State Communications》2007,141(8):440-444
Single phase ceramics CaCu3Ti4.0O12 and CaCu3Ti3.9O12 have been prepared using the traditional solid-state reaction method. Compared with the stoichiometric ceramics CaCu3Ti4.0O12, Ti-deficient ceramics CaCu3Ti3.9O12 have the larger lattice parameter, the higher force constant, and smaller dielectric constant and the lower dissipation factor, although their fundamental characters of dielectric response are similar. Their characteristic relaxation frequencies are not well fitted with the Arrhenius Law but a tentatively supposed relation. With the Cole-Cole Law, the fitted broadened factors of dissipation peaks are 0.5433 and 0.8651 for CaCu3Ti3.9O12 and CaCu3Ti4.0O12, respectively. All facts mentioned above imply that mutually correlated motion of Ti ions or defects may be expected to be responsible for the giant dielectric constant and high dissipation factor of CaCu3Ti4.0O12. 相似文献
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CaCu3Ti4O12 ceramics were prepared at the sintering temperatures ranged from 1025 to 1125 °C, and the dielectric characteristics were evaluated together with the microstructures. The giant dielectric constant with the maximum of 53,120 was obtained in CaCu3Ti4O12 ceramics at room temperature and 10 kHz, and strong processing and microstructure dependence of dielectric characteristics of the present ceramics was determined. The precipitation of the dispersed Cu-rich secondary phases of CuO and/or Cu2O and their network structure provided the extrinsic origins of the enhanced giant dielectric response, and the present findings would offer the greater potential for enhancing the giant dielectric constant and controlling the dielectric loss in CaCu3Ti4O12 ceramics by optimizing the microstructures. 相似文献
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J. Sebald S. Krohns P. Lunkenheimer S.G. Ebbinghaus S. Riegg A. Reller A. Loidl 《Solid State Communications》2010,150(17-18):857-860
In the present work we demonstrate that in addition to the well-known colossal-dielectric-constant material CaCu3Ti4O12 various members of the series Ln2/3Cu3Ti4O12 with Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm also exhibit giant values of the dielectric constant. Just as CaCu3Ti4O12, all these materials show a Maxwell–Wagner type relaxation process. For the best material, Pr2/3Cu3Ti4O12, we provide a detailed investigation of its dielectric properties in a broad frequency range up to 1 GHz. Polarization at internal barriers, most likely grain boundaries, seems to be the reason for the observed very high values of the dielectric constant. Taking into account the present results and those reported in the literature, we conclude that CaCu3Ti4O12 is not exceptional at all and there seem to be various isostructural materials with similar dielectric properties. 相似文献
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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. 相似文献
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本文研究了在真空、空气和氧气中烧结制备的三种 CaCu3Ti4O12陶瓷材料的介电特性. 交流阻抗测量结果表明在10—300 K温度范围, 三种样品的介电温谱中均出现三个平台, 其电阻实部和电容虚部在相应温度出现损耗峰, 真空条件烧结的样品具有较高的介电平台和较明显的电阻实部与电容虚部峰值, 表明氧含量和氧空位对CaCu3Ti4O12的介电性质具有重要影响, 介电温谱出现的三个平台分别源于晶粒、晶界及氧空位陷阱.温谱分析表明晶粒的激活能与烧结气氛有较大关系,氧空位引起的电子短程跳跃及跳跃产生的极化子是晶粒电导和电容的主要起源.氧空位陷阱的激活能基本与烧结气氛无关,约为0.46 eV. 氧空位对载流子的陷阱作用是CaCu3Ti4O12 低频高介电常数的重要起源. 相似文献
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Thin film of CaCu3Ti4O12 (CCTO) has been deposited on Nb-doped SrTiO3(100) single crystal using pulsed laser deposition. The dielectric constant and AC conductivity of CCTO film in the metal–insulator–metal
capacitor configuration over a wide temperature (80 to 500 K) and frequency (100 Hz to 1 MHz) range have been measured. The
small dielectric dispersion with frequency observed in the lower temperature region (<300 K) indicates the presence of small
defects in the deposited CCTO thin film. The frequency-dependent AC conductivity at lower temperature indicates the hopping
conduction. The dielectric dispersion data has been analyzed in the light of both conductivity relaxation and Debye type relaxation
with a distribution of relaxation times. Origin of dielectric dispersion is attributed to the distribution of barrier heights
such that some charge carriers are confined between long-range potential wells associated with defects and give rise to dipolar
polarization, while those carriers which do not encounter long-range potential well give rise to DC conductivity. 相似文献