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

Abstract

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 (Ts) and dwell time. Here, we achieved a large dynamic piezoelectric constant (d33*) of 510 pm/V under a very low electric field of 15–30 kV/cm. Moreover, an enhanced static piezoelectric constant (d33) of 335 pC/N was obtained with a high Curie temperature (TC) of 315 °C. The large d33 and d33* simultaneously with high TC 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.