Structural and ferroelectric properties of textured KNN thick films prepared by sol-gel methods

Based on the templates of sheet-like KNN powders synthesized by a hydrothermal method, lead-free textured KNN films with a thickness of 5 μm were prepared by sol-gel methods. The composition, microstructure, crystal structure, ferroelectric properties and grain growth mechanisms of the textured KNN thick films were studied. It was found that the KNN thick films possessed large grain sizes, dense morphology and increased ratio of Na⁺. After annealed at 650 °C, the perovskite structure was observed in the KNN thick films textured along the <00l> crystallography direction with an orientation factor of 0.393, reflecting a preferential growth characteristics. Furthermore, the residual polarization value of 12.3 µc/cm² was achieved under the same condition.