Simultaneous enhancement of piezoelectricity and temperature stability in (K,Na)NbO3-based lead-free piezoceramics by incorporating perovskite zirconates

(K,Na)NbO3 is a leading lead-free piezoelectric system, but its thermal instability of high piezoelectricity is still one of its shortcomings compared to its lead-containing counterparts. This work found that incorporating perovskite compounds with Zr ions at the B-site can lead to the simultaneous enhancement of piezoelectricity and thermal stability. The piezoelectric coefficient d(33) increased to similar to 450 pC N-1, and such a high d(33) value can be maintained within 10% change over a wide temperature range of 22-80 degrees C. The piezoelectric strain also reached 0.13% strain with a small variation (<10%) from room temperature to 130 degrees C. The intrinsic and extrinsic contributions to the piezoelectric effect were determined using a modified Rayleigh law as well as systematic analyses on the crystalline structure and electrical properties. A phenomenological interpretation is provided for the origin of the strong piezoelectricity and thermal stability in the diffused O-T phase transition. This study provides a new paradigm for the enhancement of electrical properties and thermal stability in lead-free piezoceramics.