Dielectric relaxation and conductivity in lead-free sodium bismuth titanate ceramics

Perovskite structured Na_0.5Bi_0.5TiO₃ (NBT) ceramics were synthesized by the solid-state sintering method. The presence of constituent phases and crystalline structure of the system was confirmed by X-ray diffraction technique exhibiting perovskite structure with rhombohedral symmetry. The dielectric behavior showed a broad peak at ~400°C characterized as Curie temperature. The real part of impedance (Z\´) as a function of frequency has higher values at lower frequencies and decreases up to 20 kHz and attains a constant value beyond that frequency. The broadening of peaks in frequency explicit plots of imaginary part of impedance (Z") suggests that there is a spread of relaxation times, which involves more than two equilibrium portions. The purpose of giving dielectric data obtained from the impedance studies is to give the usefulness of the impedance formalism to evaluate the dielectric behavior in the present sample. The Nyquist plot and conductivity studies showed the NTCR character of NBT ceramic samples.