Oxygen Vacancy Relaxation and Domain Wall Hysteresis Motion in Cobalt-Doped Barium Titanate Ceramics

Mechanical and dielectric loss measurements were carried out in the BaTiO3 ceramics doped with Co at frequencies between 0.01 Hz and 1 MHz as a function of temperature from −150° to 150°C. The relaxation peak observed in the ferroelectric phase with an activation energy of 0.27 eV is assumed to be related to the motion of oxygen vacancies. This peak could be because of the reorientation of an electrical dipole made of oxygen vacancies and Co3+ ions in the lattice. Furthermore, another loss peak located just below the Curie temperature Tc could be interpreted as hysteretic motion of the domain walls in a regime where the domain wall density is changing.