High remnant polarization and low coercive field of (Bi 0.5 Na 0.3 K 0.2 )TiO 3 -(Ba 0.8 Ca 0.2 )TiO 3 -BiFeO 3 ceramics with in situ domain structure at high temperature

In this work, the effects of (Ba 0.8 Ca 0.2 )TiO 3 (abbreviation BCT) addition on microstructure and electrical properties of (0.9- x ) (Bi 0.5 Na 0.3 K 0.2 )TiO 3 - x (Ba 0.8 Ca 0.2 )TiO 3 -0.1BiFeO 3 Pb-free ceramics ( x = 0.0, 0.025, 0.05, 0.075, and 0.1) were investigated. Single-phase perovskite structure and high density have been obtained in all sintered ceramics. The crystal structure was found to change from tetragonal ferroelectric to pseudo-cubic relaxor with a modification in the grain morphology from cubic to round shape with increasing BCT content. Rietveld refinement was performed for detection of the morphotropic phase boundary formed (MPB). The phase crossover is caused by lattice distortion and oxygen vacancies at high content of BCT. In situ phase formed and domain structure-dependent temperature were researched by XRD and TEM, from RT-400 °C. The domain structure was observed to change from ferroelectric polar micro-region (PMR) at RT to relaxor polar nano-region (PNR) at 200 °C caused by compositional fluctuation and then to paraelectric phase at 400 °C. And the results were confirmed by XRD at diff T . Enhanced dielectric properties with highest permittivity value were achieved at x = 0.075 due to form MPB. High value of remnant polarization (Pr = 37 µC/cm 2 ) and low value of coercive field (18 kV/cm) were observed at x = 0.075 due to the introduction of BCT. Four peaks were found in the current–electric field behavior (I-E) loops of all ceramics testifying the presence of electric-field-induced transitions.