中文摘要：

采用固相反应法制备了CaCu3Ti4-xNbxO12（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行为外,室温下在40Hz—10kHz低频率范围内还存在一个新的德拜弛豫峰,低于该弛豫特征频率时介电常数达106以上,该峰的特征频率随着Nb含量的增大向高频方向移动.根据阻抗谱中观察到的三个半圆弧,采用阻挡层电容模型,利用含有三个RC的等效电路对上述实验现象作了合理解释.

英文摘要：

The CaCu3Ti 4-x NbxO 12 （x=0,0.01,0.04,0.08,0.2） ceramics have been prepared by solid-state reaction. The XRD of the sintered ceramics indicated that complete solutions are formed for all compositions x. Dielectric properties have been investigated in the frequency range from 40Hz to 110MHz. Compared with the un-doped CCTO sample,a Debye-type dielectric relaxation has been observed for the Nb-doping CCTO samples in the frequency range from 40Hz to 10kHz at room temperature,apart from the one already known in the frequency range higher than 10kHz. Moreover,the dielectric constant reaches 106 below the characteristic frequency of the lower frequency dielectric relaxation peak which shifts to higher-frequency with increasing Nb content. The experimental results are well explained in terms of the barrier layer capacitance model and an equivalent circuit containing three RC elements by showing three semicircles in the impedance spectroscopic plane.