Large size lead-free (Na,K)(Nb,Ta)O₃ piezoelectric single crystal: Growth and full tensor properties

Environmental friendly piezoelectric single crystal, Ta-modified (K,Na)NbO₃ with the size of 12 × 11 × 11 mm³, has been successfully grown using the top seeded solution growth technique. This orthorhombic phase (K,Na)(Nb,Ta)O₃ single crystal is the largest size to date in KNN-based crystals with homogeneous composition. The large size allowed us to apply the domain engineering technique to further enhance its piezoelectric properties. In addition, a self-consistent complete set of elastic, dielectric and piezoelectric constants for the [001]_c poled domain engineered crystal has been measured, which is urgently needed for theoretical studies and simulation designs of electromechanical devices using this lead-free piezoelectric material. The electromechanical coupling factors are very high (k₃₃ = 0.827, k_t = 0.646) and the dielectric loss tangent is as low as 0.004 for this lead-free piezoelectric crystal. Such excellent properties make this crystal an excellent candidate to replace lead-containing piezoelectric materials in electromechanical devices.