简化共沉淀法制备CaCu3Ti4O12陶瓷及其介电性能研究

Dielectric properties of CaCu_3Ti_4O_(12) ceramics prepared by a simplified coprecipitation method

具有巨介电常数的CaCu_3Ti_4O_(12)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CaCu_3Ti_4O_(12)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CaCu_3Ti_4O_(12)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.

Precursor powder of CaCu3Ti4O12 is prepared by a simplified coprecipitation process, in which an optimum reaction condition with ammonium acetate is used as buffer solution and pH -- 3.0 is proved by X-ray diffraction and scanning electron microscope. The CaCu3Ti4O12 ceramics samples are prepared by sintering the calcined powder at different temperatures （1040 ℃-1100 ℃）. It is found that higher sintering temperature of CaCu3Ti4O12 ceramics will lead to lager grain size, higher dielectric constant and lower dielectric loss. The dielectric loss of CaCu3Ti4O12 ceramics is suggested to be due to DC electric conductivity, low-frequency relaxation loss and high-frequency relaxation loss. The low-frequency and high-frequency relaxations are related to grain boundary and oxygen vacancy defects respectively.