Ferroelectric domain structure of lead-free potassium-sodium niobate ceramics

The complex domain structure of orthorhombic (K0.5Na0.5)NbO3 (KNN) piezoelectric ceramics has been studied by SEM. The study was performed in samples prepared by microwave-hydrothermal synthesis. The identification of the domain structure has been afforded in KNN ceramics. Abnormal grain growth was observed in the microstructure of KNN ceramics, with an average grain size of 63 μm. Most of the ferroelectric domains were 90° type with square-net and herringbone structures alternating a–a and a–c configurations. In addition, 180° domains were also identified arranged in the common watermark pattern.