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 d33 and k33, increases the depolarization temperature Td and decreases the dielectric loss. Dielectric study showed the existence of a diffuse phase transition at Tm ≈ 320°C. It was shown that a prior electric field poling process changes the character of ϵ(T) and tanδ(T) functions, as well as shifts of Td and Tm 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. [ABSTRACT FROM AUTHOR]