batio3陶瓷晶粒结构及尺寸效应的理论分析word格式论文.docx

By introducing a parameter η the surface charge compensation factor, the long-range Coulomb interaction energy and the domain wall energy incorporated into the Landau-Ginzburg free-energy density, the relationship between ferroelectricity and grain size in nano-BaTiO3 ceramics can be calculated. Then the domain wall motion contribution to the dielectric constant is discussed. The results show that when the grain size reduces to the critical size, long-range Coulomb interaction weaking dramatically results in the instability of the ferroelectric phase. Taking into account the effects of domains, the room temperature dielectric constant of BaTiO3 particles shows a maximum value at some grain size above the ferroelectric critical size.On the basis of Poissons equation, a three-dimension comprehensive and quantitative model for semiconductive BaTiO3 ceramics was first established, after the migration of the donors, acceptor, electrons and holes has important influence on the grain boundary effect were considered. By setting a differential equation of electron level, Energy band chart was obtained by solving the equation with Runge-Kutta method. The positive temperature coefficient effect of semiconductive BaTiO3 ceramics with different grain sizes and different donors and acceptors doping were computed quantitatively. It was found that the resistivity forms a U-shaped curve with the donor concentration increasing. The resistance jumping shows a maximum at a certain acceptor doping concentration and grain size.The non-linear Current-voltage characteristics of BaTiO3 semiconductor ceramics were studied by the method of tilted energy band and continuous medium seperately at one-dimensional case. The characteristics of the grain boundary were researched. The resistance jumping is reduced with increasing electric field applied; current and voltage relation follows Ohm’s law below Curie temperature, and exhibits strong non-linear above Curie temperature; the non-linear coeff