低压二氧化钛压敏陶瓷的分析-材料学专业论文.docxVIP

华中科技大学硕士学位论文 华 中 科 技 大 学 硕 士 学 位 论 文 II II ABSTRACT Ti02 ceramic varistors, a kind of semiconductor, have low breakdown voltage, excellent non-linear coefficient and high dielectric constant. They have been widely utilized, mainly being used as transient high-voltage protector and surge arrestor. First,according to the development and recent status of Ti02 varistors,the present market prospect and the trend of development are overviewed in the paper. The electronic structure，including band structure，density of states(D0S) of rutile TiO2 is calculated from the first principles of plane wave ultra-soft pseudo-potential technology based on density function theory ，The calculated results reveal that the Fermi level moves into the conduction bands due to the many electrons doping of Nb、Sb-doped TiO2 doping concentration has a greater effect on the conductivity of system. The electrical properties and technologies of Ti02 varistors are discussed in detail. some useful experiment results have attained.we discussed the influence of trivalent low melting point oxide such a Sb2O3 on the characteristics of TiO2·Nb2O5 apacitor- varistor. Using I-V analysis and dielectric mea surement , we analyzed their working mechanism with relative theory. We found that doping this kind of oxide properly were beneficial to the grain growth and fomation of grain boundary , to enhance the non-linear coefficient and stability of the sample’s ,as well as to improve the sample’s sintering performance . The effect of Sb2O3 doping (0.１-1.0mol%) on the nonlinear electrical behavior and dielectric properties of TiO2·Nb2O5-based ceramics has been investigated. The results show that the sample containing 0.6mol% Sb2O3 has the highest nonlinear coefficient α of 6.64and varistor voltage V1ma=2.1 V.mm  . As the increase of the amount of Sb O3, -1 2 5the dielectric constant（measured at 1kHz）of samples first drop and then increase.The sample containing 0.6mol% Sb2O3 has the lowest dielectric constant(5.0