Electric properties of Mn-substituted Na0.5Bi0.5TiO3 ceramics in unpoled and poled states

The Mn-substituted NBT ceramics were prepared by the conventional ceramic fabrication technique. X-ray diffraction (XRD) studies indicated the formation of perovskite phase with rhombohedral symmetry and with small amount of second phase. It was found that 0.5mol% and 0.1mol% dopant concentration enhances piezoelectric coefficients of d(33) and k(33), increases the depolarization temperature T-d and decreases the dielectric loss. Dielectric study showed the existence of a diffuse phase transition at T-m approximate to 320 degrees C. It was shown that a prior electric field poling process changes the character of epsilon(T) and tan delta(T) functions, as well as shifts of T-d and T-m to higher temperature. The effects are mainly caused by the reinforcement of polarization/domain ordering and by the change of content rhombohedral/tetragonal phases by electric field action. The results were discussed in terms of lattice distortion and change of defect concentration.