ABSTRACT The phase-transition temperatures and piezoelectric properties of x(Bi1/2Na1/2)TiO3-y(Bi1/2Li1/2) TiO3-z(Bi1/2K1/2)TiO3 [x + y + z = 1] (abbreviated as BNLKT100y-100z) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures Td, rhombohedral-tetragonal phase transition temperature TR-T, and dielectric-maximum temperature Tm were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100y-100z show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor k33, piezoelectric constant d33 and Td of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171°C, and 0.590, 190 pC/N, and 115°C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d33, the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d33 and Td of BNLKT4-28 were 135 pC/N and 218°C, respectively. Moreover, this study revealed that the variation of Td is related to the variation of lattice distortion such as rhombohedrality 90-α and tetragonality c/a.
Digital Object Identifier 10.1109/TUFFC.2007.566
© 2007, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.