High piezoelectric performance in lead-free (K, Na)NbO₃ ceramics under a low driving field

In this work, lead-free (K0.485Na0.485Li0.03)Nb0.8Ta0.2O3 composition was designed to control the orthorhombic-tetragonal phases boundary near the room temperature as confirmed by Rietveld analysis, high-angle annular dark field scanning transmission electron microscopy, and temperature dependent dielectric constant. A comparative study of the direct and indirect synthesis methods was carried out and their functional properties were optimized as a function of sintering temperature (T-s) and dwell time. Here, we achieved a large dynamic piezoelectric constant (d(33)*) of 510 pm/V under a very low electric field of 15-30 kV/cm. Moreover, an enhanced static piezoelectric constant (d(33)) of 335 pC/N was obtained with a high Curie temperature (T-C) of 315 degrees C. The large d(33) and d(33)* simultaneously with high T-C in a single composition are promising results in lead-free polycrystalline ceramics. The strategic design of this work opens a new door for the possible development of novel functional materials for device applications.