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首页> 外文期刊>Physical review >Evidence of the ultrahigh dielectric constant of CaSiO_3-doped CaCu_3Ti_4O_(12) from its dielectric response, impedance spectroscopy, and microstructure
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Evidence of the ultrahigh dielectric constant of CaSiO_3-doped CaCu_3Ti_4O_(12) from its dielectric response, impedance spectroscopy, and microstructure

机译：CaSiO_3掺杂的CaCu_3Ti_4O_（12）的超高介电常数从其介电响应，阻抗谱和微观结构的证据

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摘要

The temperature and frequency dependences of the dielectric responses and the complex impedance spectra of polycrystalline CaCu_3Ti_4O_(12) (CCTO) doped with CaSiO_3 have been investigated. The dielectric responses show two Maxwell-Wagner-type relaxations including insulating layers of grain boundaries and domain boundaries and semiconducting grains. The behavior of the temperature dependence of the dielectric constant at 1 kHz is demonstrated to be determined by the frequency dependence of the dielectric constant of two superposed dielectric relaxations at different temperatures. In contrast to the undoped CCTO, an extra semicircle clearly appears in the complex impedance plots of CaSiO_3-doped CCTO. The results further confirm the presence of the domain boundaries, and their resistivity is lower than that of the grain boundaries. The microstructures have been characterized and the compositions of the grains, grain boundaries, and the second phases have been determined quantitatively. The Si ions are proved to be segregated to the grain boundaries. The grain-boundary phases consist of a main Si-rich amorphous phase and a small amount of nanosized Cu-rich particles. The Cu-rich particles are present at grain edges or corners of the microstructures. The variations of the electrical conduction and the dielectric responses are related to the reduction of the concentration of the excess Cu ions along the grain boundaries.
机译：研究了掺杂CaSiO_3的多晶CaCu_3Ti_4O_（12）（CCTO）的介电响应的温度和频率依赖性以及复阻抗谱。介电响应显示出两个麦克斯韦-瓦格纳型弛豫，包括晶粒边界和畴边界的绝缘层以及半导体晶粒。介电常数在1 kHz时的温度依赖性行为证明是由两个在不同温度下叠加的介电弛豫的介电常数的频率依赖性决定的。与未掺杂的CCTO相比，CaSiO_3掺杂的CCTO的复数阻抗图中明显出现了一个额外的半圆。结果进一步证实了畴边界的存在，并且它们的电阻率低于晶界的电阻率。表征了微观结构，并定量确定了晶粒，晶界和第二相的组成。事实证明，硅离子偏析在晶界上。晶界相由主要的富硅非晶相和少量的纳米级富铜颗粒组成。富含铜的颗粒存在于微结构的晶粒边缘或拐角处。电导率和介电响应的变化与沿晶界的过量Cu离子浓度的降低有关。

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