The engineered domain configuration was induced into potassium niobate (KNbO3) crystals, and the piezoelectric properties were investigated as a function of domain size. First, single-domain treatment was investigated, and a combination of chemical etching and 2-step electric poling treatment was effective. Using the single-domain crystals, all piezoelectric related constants were determined. On the basis of these piezoelectric constants, the d 31 and d 32 surfaces were calculated. The piezoelectric properties of [001] c oriented KNbO3 single-domain crystals were measured and were completely consistent with the calculated properties. Finally, the engineered domain configurations were induced into KNbO3 crystals by the control of the temperature and the electric-field along the [001] c direction. The piezoelectric properties of these KNbO3 crystals with the engineered domain configurations showed much higher values than those of the single-domain crystal. Moreover, the piezoelectric properties increased with decreasing the domain sizes of the engineered domain configuration.

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