Temperature dependence of polarization and strain of bismuth-based ceramic composites

We investigated the temperature-dependent polarization and strain of two Bismuth-based perovskite composites. Matrix material was chosen as 0.94Bi 0.5 (Na 0.75 K 0.25 ) 0.5 TiO 3 -0.06BiAlO 3 (BNKT-BA) which have a transition from relaxor to ferroelectric phase (T R-F ). Seed materials were Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 (BNKT) and 0.985Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 -0.015BiAlO 3 (BNKTBA), which possessing different polarization characteristics. Depending on the test temperature, the different polarization and strain behaviors were observed between the BNKT-BA/BNKT and BNKT-BA/BNKT BA composites. At T = 25 °C, the two composites (BNKT-BA/BNKT and BNKT-BA/BNKTBA) exhibited double-like polarization loops and parabolic strain curves which involve an ergodic relaxor-to-normal ferroelectric phase transition with external electric field and a reverse ferroelectric-to relaxor phase transition with removal of the field. At T = 120 °C, two composites have slim polarization and strain curves, which are almost the same as those of the pure BNKT-BA. The high field-induced polarization and strain with respect to temperature for the composites are related to the thermal stability of the ferroelectric seeds, and the nucleation and growth of ferroelectric domain in the relaxor matrix.