Enhanced Ferroelectric and Converse Piezoelectric Properties of Dense Lead-Free Na0.4K0.1Bi0.5TiO3 Ceramics for Actuator Applications

In this work, lead-free Na0.4Bi0.5 TiO3-K0.1Bi0.5TiO3 (NKBT) piezoelectric ceramics were prepared by the solid-state reaction method and their structural, ferroelectric and dielectric properties were systematically studied. NKBT sintered at 1150℃ for 4 h exhibited highly dense (96% - 98% of the theoretical density) and uniform grains of size 1.1 μm. The coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases due to the presence of morphotrophic phase boundary for the chosen composition has been confirmed by the Rietveld refinement studies. Enhanced ferroelectric properties such as remnant polarization (Pr) and coercive field (EC) are found to be 37 μC/cm2 and 30 kV/cm, respectively. The optimized synthesis procedure for NKBT ceramics resulted in enhanced strain (%) and converse piezoelectric coefficient (d33*) of 0.3 % and 554 pm/V which is attributed to smaller grain size and switching of non 180o domains. NKBT ceramics with such excellent piezoelectric properties can be considered as a promising candidate for actuator applications.