A high quality lead-free (Li, Ta) modified (K, Na)NbO3 single crystal and its complete set of elastic, dielectric and piezoelectric coefficients with macroscopic 4mm symmetry

摘要

A high quality orthorhombic (K, Na, Li)(Nb, Ta)O-3 single crystal with a large size of 9 x 9 x 11 mm(3) was successfully grown using the top-seeded solution growth method. Its large size allowed us to perform comprehensive investigation on this crystal. A complete set of elastic, dielectric and piezoelectric coefficients was determined using combined resonance and ultrasonic methods. The longitudinal piezoelectric coefficient d(33) and the transverse piezoelectric coefficient d(31) of this lead-free piezoelectric single crystal are as high as 354 pC N-1 and -163 pC N-1, respectively, which are two times higher than those of KNN-TL ceramics and are comparable with those of PZT5. The electromechanical coupling factor k(33) is as high as 82%, much higher than those of KNN-TL ceramics and PZT5. The coefficient d(33,strain) was found to be as high as 672 pm v(-1) and the extrinsic contribution (similar to 22%) was investigated by Rayleigh analysis. These high piezoelectric properties make this single crystal a promising candidate for replacing lead-based piezoelectric materials.