Microwave dielectric relaxation process in doped-incipient ferroelectrics

The electrical permittivity properties in the microwave frequency range were investigated in incipient and relaxor compositions of Sr1−xCaxTiO3 ceramics from 60 to 440 K. The results revealed that the origin of microwave dielectric relaxation process lies in the appearance of nanometric polar regions rather than any other ferroelectric or piezoelectric mechanism. The experimental data also showed that the relaxation frequency is reasonably independent of the correlation length. The occurrence of more stable polar phase into the grain bulk induced by dipole moment related to the grain boundaries was also verified.