Study On Dielectric Behavior Of Ba(Ti_0.9Zr_0.1)O₃ Ceramics

Barium titanate(BaTiO₃) ceramics are the main raw materials of high dielectric ceramic capacitors, with a typical perovskite (ABO₃) structure, high dielectric constant, good ferroelectric, piezoelectric, voltage and insulation resistance. BaTiO₃-based relaxor ferroelectric ceramics are provided with high dielectric constant, the appropriate phase transition temperature and easy relaxation ,etc.They are accomplished with the main materials of multilayer ceramic capacitors, but also the main materials of the theory of relaxor ferroelectrics Therefore, the study of relaxor properties on BaTiO₃ ceramic has become hot spots and focus.In this paper, Ba(Ti_0.9Zr_0.1)O₃ ceramics has been selected as basis and prepared by the conventional ceramics preparation technique.From the angle of ion valence and radius,the effect of the structure ,dielectric properties and ferroelectric properties of Ba(Ti_0.9Zr_0.1)O₃ ceramics doped with additive has been investigated.The main results are as follow:1. The influence of the structure and dielectric properties of Ba (Ti_0.9Zr_0.1) O₃ ceramics doped with Bi₂O₃ has been studied. X-ray diffraction patterns indicate that 3% (in mole)of Bi³⁺ doping can be fullly incorporated into the perovskite lattice of Ba(Ti_0.9Zr_0.1)O₃.And these ceramics are transition to relaxor ferroelectrics from diffuse ferroelectrics.Then, Ba_0.98Bi_0.02(Ti_0.9Zr_0.1)O₃ ceramics are selected as basis ,and the different valence ions are doped at B site such as Cu²⁺, Co³⁺, Sn⁴⁺, V⁵⁺ and Mo⁶⁺, of which the radius is similar with (Ti⁴⁺,Zr⁴⁺.) The research results show that,to a certain extent,the crystallite size becomes smaller.When the valence of doped ions is less than four ,and the local random field which caused by the valence difference and defect is relatively strong,the behavior of dielectric relaxation is obvious;while the local random field is weak,this behavior can not easily be observed. When the valence of doped ions is equal four,it has little effect of dielectric properties. When is more than four,the degree of dielectric relaxation is slightly lower.2.The influence of the structure and dielectric properties of Ba(Ti_0.9Zr_0.1)O₃ ceramics co-doped with Mo-Mn and Mo-Cu has been studied. The research results show that the ceramics grain refinement are improved ,and the characterstics of diffuse phase transition ferroelectric by the whole ceramics are performaced.Meanwhile,the relaxation phenomenon is not obvious.The dielectric loss is substantially lower when co-doped with Mo-Mn.Both co-doped with Mo-Mn and Mo-Cu, the hysteresis loop shows a generally shrinking effect.