Investigation Of PTC Effect In BaTiO₃ Ceramic Modified By Pr/Mn

In order to get high performance PTC material,different kinds of Pr/Mn modified BaTiO3 powders whose doping mole fraction was 0.001, 0.002, 0.003, 0.004, 0.005 and 0.006 separately were prepared by sol-gel method. The prepared powders were analyzed by TEM,the grain sizes were about 30nm and the grains distributed equalitily.Then the powders were sintered for preparing ceramics,the sintered ceramics were penetrated by Pr,Mn,Pr fistly and then Mn,Mn firstly and then Pr,Pr and Mn together.Then constitutes,structures.appearances and electric capability of the modified BaTiO3 ceramics were investigated.For the BaTiO3 ceramics doped by Pr, resisitivity at room temperature are all about 105m,which is much lower than that of BaTiO3 ceramic,which is 1012m;The resisitivity of the BaTiO3 ceramics doped by 0.004 mole Pr and then penetrated by Pr is the lowest ,it is 0.35m;Then the ceramic was penetrated by Mn,and the effect of the positive temperature coefficient of resistivity appeared. For the BaTiO3 ceramics doped by Mn, resisitivity at room temperature are all about 1013m,which is higher than that of BaTiO3.But the doping of Mn can increase the peak value of PTC effect. And the lowest resisitivity is 2.01m after penetration.The BaTiO3 showed the effect of negative temperature coefficient of resistivity after it was penetrated by Pr and Mn together,and the resistivity could decrease from 104 mto 102 m.The results of XRD test showed that ,the perovskite structure of BaTiO3 penetrated by Pr/Mn did not change obviously.The results of XPS test showed that ,the correspond element and the element carbon were found in the BaTiO3 after it was penetrated, and the binding energys of Ba,Ti and O were all increased 2eV than those in the pure BaTiO3 ceramic,but those in the BaTiO3 ceramic doped by Pr or Mn were all increased 11eV. All of these indicated that the method of gas penetration could make the elements into the cramics.The results of SEM test showed that,after pentration of Pr or Mn,the gowth of the BaTiO3's grain was more integrity , the grains distributed equally and the porosity declined.