A correlated electron diffraction, in situ neutron diffraction and dielectric properties investigation of poled (1-x)Bi_0.5Na _0.5TiO₃-xBaTiO₃ ceramics

A correlated electron diffraction, temperature-dependent in situ neutron diffraction, and temperature-dependent dielectric properties investigation of poled (1-x)Bi_0.5Na_0.5TiO₃-xBaTiO₃ (BNTBT100x) (x = 0.04, 0.07, and 0.12) samples has been carried out. The results show that the depolarization temperature, T_d, of the rhombohedral BNTBT 4 sample is associated with the disappearance of G ± - [111]*_p satellite reflections and a^-a ^-a^- octahedral tilting while that of the BNTBT 12 sample is associated with a metrically tetragonal to metrically cubic or pseudo-cubic symmetry. In the case of the poled BNTBT 7 sample in the MPB region, the dielectric properties show a quite distinct two stage transition from a room temperature clearly metrically tetragonal phase again to a metrically cubic or pseudo-cubic symmetry above 150 °C. There is no apparent change in its average structure in vicinity of T_d in BNTBT 7. Electron diffraction shows the presence of considerable octahedral tilt twin disorder in all three samples.