Fe掺杂CaCu_3Ti_4O_(12)陶瓷的介电性能与弛豫特性研究

Study on the dielectric properties and dielectric relaxation of Fe-doped CaCu3Ti4O12 ceramics

采用固相反应法制备了CaCu3Ti4-xFexO12(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:CaCu3Ti4-xFexO12陶瓷在x取值范围内形成了连续固溶体.随着Fe含量x的增加,晶粒半导性逐渐消失,介电常数减小.当x≤0.04时,在106—108和103—104Hz频率范围存在介电弛豫行为Ⅰ和介电弛豫行为Ⅱ,高频介电弛豫行为Ⅰ与陶瓷内的晶界阻挡层有关,而低频介电弛豫行为Ⅱ与陶瓷表面层发生的界面极化有关.在CaCu3Ti3.99Fe0.01O12陶瓷的高温频谱中,观察到了第三个介电弛豫行为Ⅲ,它与局域电荷的跃迁有关,利用阿列纽斯关系式得到此过程的热激活能0.78eV.

The CaCu3Ti4-x Fex O12 （0 ≤ x ≤0.2） ceramics have been prepared by a standard solid-state reaction method, and the influence of Fe doping on the microstructure and dielectric properties of CaCu3 Ti4-x Fex O12 ceramics were investigated by the Xray diffraction, scanning electron microscopy, dielectric spectroscopy and impedance spectroscopy. It has been found that complete solid solutions are formed for all of the compositions x. With the increase of Fe content, the semiconductivity of grain vanishes gradually and the dielectric constant decreases. For specimens with x ≤ 0.04, the two dielectric relaxation process I and Ⅱ appeared in the frequency ranges of 106-10s and 103-104 Hz, respectively. These two dielectric relaxation process were considered to be associated with grain boundaries and interfacial polarization between the electrode and ceramic surface, respectively. In addition, the third dielectric relaxation Ⅲ was detected in the high-temperature dielectric spectroscopy of CaCu3 Ti3.99 Fe0.01 O12 ceramic, which was caused by a hopping process of localized charge carriers. The activation energy of this thermally excited relaxation is 0.78 eV, as obtained by using the Arrhenius formula.