Effect of Amount of Polyvinylpyrrolidone Introduced in Solution-Derived Ferroelectric K0.5Na0.5NbO3 Thick Films

Abstract

Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thick films were successfully prepared by polyvinylpyrrolidone (PVP)-modified chemical solution deposition method. The effect of PVP amount on structures and electrical properties of KNN thick films has been investigated. Thickness of the films is in a range of 0.70 and 4.35 μm depending on the addition amount of PVP in the precursor solutions. All the films show pure perovskite phase. The X-ray photoelectron spectroscopy analysis indicates that PVP has a negligible effect on KNN films when the addition amount is smaller than 0.25. While the increasing amount of PVP can promote the formation of the perovskite phase. The surface morphologies are dense except KNN films with the ratio of PVP monomer to KNN of 1.25. The KNN films with the ratio of PVP monomer to KNN of 1.0 exhibit large dielectric constant of 662 at 1 kHz and the saturated polarization-electric field hysteresis loops. Even though KNN thick films with the ratio of PVP monomer to KNN of 1.25 show the porous morphology, the largest piezoelectric constant d 33 of 62 pm/V is obtained.