NaNbO3 templates-induced phase evolution and enhancement of electromechanical properties in <00l> grain oriented lead-free BNT-based piezoelectric materials

Recently developed Bi0.5Na0.5TiO3(BNT)-based piezoceramics face two urgent obstacles: high driving field required to trigger large strain and poor temperature stability. Highly oriented (1-x)(0.83Bi0.5Na0.5TiO3-0.17Bi0.5K0.5TiO3)-xNaNbO3 (BNT-BKT-xNN) piezoceramics were synthesized using NN templates to resolve both obstacles. Measurements of polarization and strain hysteresis loops as well as phase transition temperature revealed a phase evolution from ergodic relaxor to ferroelectric phases, generating a high strain of 0.43% and large Smax/Emax = 720pm/V for textured BNT-BKT-4NN ceramics. The field-dependent strain was largely depended on the degree of texturing. Most intriguingly, grain-oriented specimens provided excellent actuating performance characterized by both large Smax/Emax = 693 pm/V at a low driving field of 45 kV/cm and enhanced temperature stability with Smax/Emax = 537pm/V at 120 °C. This was basically ascribed to the facilitated switching between ergodic relaxor and ferroelectric phases owing to the grain-oriented structure. As a consequence, design of <00l> oriented microstructure opens the possibility to produce efficient BNT-based piezoceramics for transferral into real-world applications.