Dielectric, ferroelectric, piezoelectric, and electrostrictive properties of K0.5Na0.5NbO3 single crystals

The dielectric, ferroelectric, piezoelectric, and electrostrictive properties of K0.5Na0.5NbO3 single crystals (KNN s.c.) prepared by solid-state crystal growth are reported. The dielectric constant (epsilon), dielectric losses (tan delta), remanent polarization (P-r), and coercive field (E-c) for KNN s.c. in the [1(3) over bar 1] direction at room temperature are 1015, 1%, 17 mu C/cm(2), and 24 kV/cm, respectively. The influence of 180 degrees domains to the linear piezoelectric response and quadratic electrostrictive response of KNN s.c. is discussed. The piezoelectric coefficient d(33) and the electrostrictive coefficient M-33 of KNN s.c. measured using atomic force microscopy at 2 Hz was 80 pm/V and 2.59x10(-14) m(2)/V-2, respectively. The extremely high M-33 value can be explained by the extrinsic strain from the domain-wall motion. The properties of the surrounding polycrystalline KNN ceramic are added for comparison.