Mg在BaTiO_3瓷中抗还原机理研究

Mechanism of Anti-reduction by Mg in BaTiO_3 Ceramics

研究Mg在BaTiO3瓷中的抗还原作用。采用CO、CO2还原气氛中烧结制作不同含Mg量(摩尔分数为0.05%～0.25 %)BaTiO3瓷试样。实验结果表明含Mg的BaTiO3瓷比不含Mg的BaTiO3瓷体积电阻率高8～9数量级。试样XRD谱线计算,晶胞参数a,c随Mg含量的增加而增大,电子探针显示Mg均匀分布。显微结构分析推断,Mg既固溶于A位(MgBa)又固溶于B位(MgTi),杂质缺陷结构(MgTI)的受主电离复合还原气氛产生的氧缺位(VO)的施主电离,从而大大降低了施主电离的电子浓度。因此,MgTi的存在是BaTiO3瓷抗还原的本质。

To find the mechanism of anti-reduction by Mg in BaTiO3 ceramics, samples of BaTiO3 ceramics of different Mg content were sintered in the CO or CO2 atmosphere. The result shows that ρv of the samples with Mg is 109~10 cm while that of pure BaTiO3 ceramics is 101~2 cm. The X-ray analysis result demonstrates that the lattice parameters increases with the increase of Mg concentration. The EPMA analysis result illustrates the Mg distribution in the BaTiO3 ceramics is uniform. It is concluded that Mg is not only locates in the A position (MgBa), but also in B position (MgTI), and that defect of MgTI ionization can produce the hole and composite the oxygen vacancy when BaTiO3 sintered in reduction atmosphere. Therefore, the concentration of the electron decreased. It is Mg located in the B position that BaTiO3 ceramics can resist the reduction, that is, the existence of MgTI.