Solid-state conversion of (Na1/2Bi1/2)TiO3-BaTiO3-(K1/2Na1/2)NbO3 single crystals and their piezoelectric properties

Piezoelectric ceramic with a composition of (94-x)(Na1/2Bi1/2)TiO3-6BaTiO(3)-x(K1/2Na1/2) NbO3 (NBT-BT-xKNN) is a promising lead-free piezoelectric material for actuator applications because of its giant electric-field-induced strains, which are comparable with that of soft Pb(ZrxTi1-x)O-3 (PZT) ceramics. Using the solid-state single crystal growth method, we succeeded in fabricating usable single crystals of NBT-BT-3KNN (6 mm x 6 mm x 8 mm size) with a uniform chemical composition. The room temperature piezoelectric properties of < 001 >, < 110 >, and < 111 > oriented single crystals were measured. Single crystals showed strong anisotropic strain characteristics. In particular, < 001 > oriented single crystals had excellent piezoelectric properties with small hysteresis and a high strain of 0.57% at 7 kV/mm. In addition, the fabricated single crystals exhibited a high converse piezoelectric constant, S-max/E-max, of over 1000 pm/V at 4 kV/mm. These values are greater than those reported for any lead-containing and lead-free ceramics and comparable with those of lead-based single crystals. Our investigation demonstrates the solid-state conversion of lead-free single crystals and their practical usability in replacement of lead-based materials. (C) 2014 AIP Publishing LLC.