Ba(Fe_(0.5)Nb_(0.5))O_3/Ni复合陶瓷材料介电性能的研究

The research of dielectric properties of Ba(Fe_(0.5)Nb_(0.5))O_3/Ni composite ceramics

在氮气气氛中采用传统固相法制备了(1-x)Ba(Fe0.5Nb0.5)O3/xNi(x=0.1,0.2,0.3;BFN/Ni)复相陶瓷,并研究了Ni含量对复相陶瓷晶体结构、显微组织、渗流阈值及介电性能的影响.研究结果表明:在高温烧结过程中,Ni含量为30wt%时,BFN和Ni没有发生化学反应.BFN/Ni复合陶瓷的电阻率随着Ni含量的增加而下降,且在渗流阈值附近,复合材料从绝缘体逐渐变为导体.BFN/Ni复合陶瓷的介电常数会随着Ni含量的增加而急剧增大.在室温下1kHz条件下,当Ni含量为30wt%时,复合陶瓷材料的介电常数约为1 670 000,这是由于在导体和绝缘体的相界面处积累了大量的空间电荷,并由此产生界面极化,导致介电常数显著增大,且随着导体含量的增加,这种界面效应更加明显.对于介电常数的增加,可以借助Maxwell-Wagner极化模型来给予解释.

The BFN/Ni composite ceramics doped with Ni in the content range of 10-30 wt% were prepared by the traditional solid state reaction in nitrogen gas. The crystal structure, microstructure, percolation threshold and corresponding dielectric properties of ceramics were investigated. The findings suggest that there is no reaction took place between BFN and Ni during the sintered conditions when the Ni content was 30 wt%, which shows Ni was not incorporated into the lattice of BFN matrix. The resistivity of BFN/Ni composite ceramics decreases with Ni content increasing and then the composite is gradually changing from insulator into conductor at the percolation threshold. The value of εr of BFN/Ni composites is raised with the increase of Ni content, and the maximal value is about 1 670 000 at 1 kHz at room temperatures as Ni content of 30 wtG. The interfaces of the conductor and the insula- tor accumulated a large number of space charge caused to interracial polarization. The interra- cial effects are more significant with increasing conductor content. The dielectric behaviors of BFN/Ni composite ceramics can be explained as Maxwell-Wagner effect, which were usually adopted to explain the extremely high dielectric constant.