Comparative study of the polarization and strain of inclusion-type and layer-type 0.94Bi(NaK)TiO3–0.06BiAlO3/Bi(NaK)TiO3 ceramic composites

This study presents a comparison between the inclusion-type and layer-type ceramic–ceramic composites, consisting of relaxor and piezoelectric phases, in terms of polarization and strain behaviors. Bi(NaK)TiO3 (BNKT) and 0.94Bi(NaK)TiO3–0.06BiAlO3 (BNKT–BA) were prepared for ferroelectric and relaxor materials, respectively. In the case of the layer-type composite, the polarization and strain behaviors were observed as a function of the volume ratio of the relaxor/piezoelectric phases. With an increase in the ratio of BNKT/BNKT–BA, a larger strain was obtained with the electric field. For the inclusion-type composite, the largest saturation polarization with double hysteresis loop and large saturation strain were measured at a ratio of 0.2. Comparison of the two composites indicates that larger polarization and strain were observed for the inclusion-type composite than the layer-type composite. This may be related to the fact that the ferroelectric phase serves as a preferential nucleation/growth site for the relaxor-to-ferroelectric phase transition in the relaxor matrix, which was evaluated using the polarization dynamics of the ferroelectric materials.