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 (ε), dielectric losses (tan δ), remanent polarization (Pr), and coercive field (Ec) for KNN s.c. in the [13¯1] direction at room temperature are 1015, 1%, 17 μC/cm2, and 24 kV/cm, respectively. The influence of 180° domains to the linear piezoelectric response and quadratic electrostrictive response of KNN s.c. is discussed. The piezoelectric coefficient d33 and the electrostrictive coefficient M33 of KNN s.c. measured using atomic force microscopy at 2 Hz was 80 pm/V and 2.59×10−14 m2/V2, respectively. The extremely high M33 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.