Lead-free (K, Na)NbO₃ thin films derived from chemical solution deposition modified with EDTA

Potassium sodium niobate is an important and promising functional material due to its ferroelectric, piezoelectric, and pyro-electric properties, and have received much attention for decades. In this paper, lead-free (K, Na)NbO₃ (KNN)-based ferroelectric thin films were successfully prepared by a chemical solution approach using Nb₂O₅ as niobium resource instead of the expensive niobium ethoxide. The films with a pure perovskite phase were obtained by such an approach modified with ethylenediaminetetraacetic acid (EDTA). EDTA plays a positive role in suppressing the volatilization of alkali metal and facilitates a better film growth rate. EDTA introduction prevents the formation of the pyrochlore phase. The films synthesized with EDTA show large grains and good crystallization, indicating decreased nucleation temperature. The obtained KNN thin films exhibit low leakage current, large saturated polarization, and small coercive field. These results are attributed to the added EDTA, which is effective in inhibiting the formation of vacancies, and to the weakened effect of the defect pinning or clamping of domain walls.