Lead-free (K, Na)NbO3 ferroelectric thin films: Preparation, structure and electrical properties

Lead-free ferroelectric (K, Na)NbO3 (KNN) thin films were prepared on Pt/Ti/SiO2/Si substrate by a sol–gel method. Sodium acetate, potassium acetate and niobium pentaethoxide were used as starting metal–organic compounds in KNN precursor solutions. The thermal decomposition of KNN gel was studied by thermal analysis method. Thin films of KNN with a perovskite structure were obtained by pyrolysis at 400 °C and rapid thermal annealing at 500–650 °C. The KNN thin films showed relatively dense and uniform microstructure with grain size of about 100 nm. KNN thin films annealed at 650 °C exhibited a dielectric constant of 258 and loss tangent of 0.05, respectively, at 1 kHz. A ferroelectric hysteresis loop with a remnant polarization and coercive field of 3.54 μC/cm2 and 160 kV/cm, respectively, was obtained for the KNN thin film.

Research highlightsIn this work, sodium acetate and potassium acetate were used as starting metal–organic compounds for the preparation of KNN precursor solutions. The chemical property of KNN precursor gel was studied by thermal analysis method. The optimum pyrolysis and annealing temperatures are determined. The influence of the process parameters on the microstructure, dielectric properties and ferroelectric of KNN thin films has been investigated, respectively.