Enhanced piezoelectric properties of KNbO3 crystals by domain engineering

Potassium niobate (KNbO₃) single crystals were grown by a TSSG method. At first, the electric field was applied along [001]_c (cubic notification system) direction of KNbO₃ crystals to induce the engineered domain configurations into KNbO₃ crystals. Prior to domain engineering, the piezoelectric properties of [001]_c oriented KNbO₃ single domain crystals were measured. These measurement values were completely consisted with the calculated apparent d₃₁ and d₃₂. Finally, the engineered domain configurations were induced into KNbO₃ crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain configuration. However, the symmetry of the KNbO₃ crystals was mm2, and there were four kinds of domain structures such as 90°, 180°, 60° and 120° domains. Thus, the engineered domain structure induced in this study was very complicated, and the piezoelectric properties were also depended on domain pattern and kinds of domain walls.