Defect-dipole-induced two important macroscopic effects: The dielectric relaxation and the ferroelectric aging in hybrid-doped (Ba,Ca)TiO_3 ceramics

摘要

To observe the dielectric relaxor behavior and the ferroelectric aging effect, the structural and electrical properties of (Ba_(0.90)Ca_(0.10))(Ti_(1-x)Ca_x)O_(3-x) (BCT-C) ceramics prepared using a conventional dry route were investigated. With increased concentration of Ca on the B-site in BCT-C ceramics, the tetragonal phase is decreased while the multiphases with the cubic pervoskite structure as a major constituent is increased and remained predominant in the BCT-C ceramics with x ＞ 0.03. The increased amount of Ca on the B-site causes the high temperature phase transition to shift to the low temperature and results in an increase in the degree of diffusion and relaxation of the BCT-C ceramics. The observed dielectric relaxation behavior may be understood by a defect-dipole formed random electric field induced domain state. The aging effect controlled by the migration of mobile oxygen vacancies is rarely observed in aged BCT-C ceramics while it can be markedly observed in Bi-doped BCT ceramics. Based on the microscopic mechanism of the aging effect, the possible reasons for the aging effect are given.