La-Mn共掺杂的钛酸钡陶瓷还原再氧化研究

Investigation on Reduction and Oxidation of La-Mn Co-doped Barium Titanate Ceramics

以MnO2为受主,La2O3为施主,采用传统高温固相法对钛酸钡陶瓷进行掺杂,并对还原气氛下烧结的样品分别在900℃和1000℃的温度下进行再氧化处理。采用XRD和电性能测试研究了镧锰共掺杂和再氧化工艺对于钛酸钡陶瓷阻温特性及微观结构的影响。结果表明:钛酸钡陶瓷的阻温特性与施主、受主的掺杂比例和烧结气氛有关;与在空气下烧结相比,在还原气氛下烧结能明显的提高施主掺杂的临界浓度,同时随着再氧化温度从900℃提高到1000℃,PTC效应明显增强。BaTiO3晶粒尺寸随着施主掺杂浓度的提高而变小。Mn离子的掺入使钛酸钡晶格结构更为紧密,阻碍了晶格内部氧离子向外部的扩散,导致了明显的PTC效应。

The BaTiO3 ceramic was doped by conventional solid state processing using MnO2 doped as acceptor, La2O3 doped as donor. The samples sintered in reduing atmosphere were reoxidized at 900℃ and 1000 ℃. The influence of Mn, La co-doped on the resistance- temperature and microstrueture of the samples were investigated by the means of scanning electron microscopy and electric properties testing. The results show that the resistance-temperature properties of BaTiO3 ceramics were related with the ratio of donors and aceeptors, as well as the sintering atmosphere. The critical concentration of La-doped samples increased obviously compared with the samples sintered in air, the La-Mn doping samples appear strong PTC effect after reoxidized in air at 1000℃ compared with 900℃. The grain size decreased as the La-donor content increasing. The Mn ion soluted into BaTiO3 ceramic and made BaTiO3 lattice structure more closely. It prevented the diffusion of oxygen ions from internal lattice, and the concentration of oxygen vacant was very low, which led to the strong PTC effect.