Understanding the depolarization phenomena in (1-x) Na_0.5Bi_0.5TiO₃. (x) Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃solid solutions...

A decrease in depolarization temperature (T_d) from 456 K to 352 K was observed with an increase in BCZT substitution in the NBT for the (1-x) Na_0.5Bi_0.5TiO₃. (x) Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃solid solutions. A transition towards a higher ergodic state was elucidated with an increase in BCZT content that helped to reduce the free energy barrier, hence lesser thermal energy was required to depolarize the modified systems. Furthermore, a decrease in remnant polarization and coercive field, coupled with an increase in energy storage (W_stored) and efficiency (η%) with higher BCZT content.In-situtemperature-dependent Raman spectra provide additional insights, highlighting the faster changes in phonon shifts and lifetimes corresponding to the A-O, B-O, and BO₆vibrations around the depolarization temperature (T_d). The observed phase transformation to aP4bm phase at temperatures significantly higher thanT_dis substantiated by Raman shift and phonon lifetime variations in the modes associated with the A-O and B-O vibrations. The transitions can be understood as: atT∼T_dthe polar nano regions (PNRs) start to appear due to weakening of bonds,T>T_dall the long-range ferroelectric domains transform to PNRs converting the material to a fully ergodic state, and at much higher temperatures (T≫T_d) theR3c PNRs vanish andP4bm PNRs appear.