Composition design and electrical property of a pure KxNa1−xNbO3 single crystal fabricated by the seed-free solid-state crystal growth

Abstract

In this work, based on a composition design, a pure K0.52Na0.48NbO3 (KNN) lead-free piezoelectric single crystal with a maximum dimension of 4 mm × 4 mm × 2 mm was successfully prepared by the seed-free solid-state crystal growth method. The X-ray diffraction results indicate that the as-grown KNN single crystals have a perovskite crystalline structure with a single orthorhombic phase. An porous microstructure exists in the pure KNN single crystal in this present. The orthorhombic-tetragonal T O−T and tetragonal-cubic phase transition temperature Curie temperature T C of the single crystal are found at 190 and 424 °C, respectively. The obtained KNN single crystal exhibits a piezoelectric coefficient d 33 of 103 pC/N and relative dielectric permittivity ɛ of 180. The resistance of KNN single crystal is insensitive to the temperature in the measurement range. The conductive mechanism of the single crystal mainly comes from the grain interiors.