Effect of electrical poling on the structural, vibrational, and electrical properties of 0.94(Na0.5Bi0.5TiO3) -(0.06-x) CaTiO3-x (BaTiO3) lead-free ceramics

Sol-gel prepared 0.94(Na0.5Bi0.5TiO3)-(0.06-x) CaTiO3-x (BaTiO3) samples show a R3c phase for both the poled and unpoled materials. The lattice parameters, volume, distortion, and homogeneous strain (delta) increased with the Ba content for both the poled and unpoled cases. The poling increased the volume, c/a ratio, and lattice distortions for all the compositions. The higher Ba incorporation increased the Ti-Ti distance possibly decreasing the lattice's free energy, making it more stable. Poling induces a long-range ordering. The presence of Ba and simultaneously the effect of poling enables the lattice to transit from a more disordered to a more ordered one. Dielectric constant increased with increasing Ba incorporation. The increase in depolarization temperature (Td) with an increase in the Ba indicates the stability of the ferroelectric phase, which is also evident from the increase in the c/a ratio. The thickness electromechanical coupling factor (Kt) continuously increases from 20.64% for x = 0-35.29% for x = 0.05 composition due to the increase in the c/a ratio with Ba incorporation. The piezo-electric coefficient increases from 33 for x = 0 to 110 for x = 0.05.