Dielectric and Piezoelectric Properties of (Bi_0.5Na_0.5)TiO₃–(Bi_0.5K_0.5)TiO₃ Systems

The structural, dielectric and piezoelectric properties of [Bi_0.5(Na_1-XK_X)_0.5]TiO₃ ceramics were studied for the compositional range, X=0–1.0. The samples were prepared by a conventional sintering technique. From X-ray diffraction results, it was found that the morphotropic phase boundary (MPB) between (Bi_0.5Na_0.5)TiO₃ (rhombohedral) and (Bi_0.5K_0.5)TiO₃ (tetragonal) exists in the range of X=0.16–0.20. Polarization-Electric field hysteresis loops show that the remanent polarization at X=0.20 (BNTK20) is larger than that at X=0.0 (BNT). Peaks of electromechanical coupling factor, dielectric constant, piezoelectric constant and elastic compliance were obtained at X=0.16–0.20 of the MPB region. Dielectric and piezoelectric properties are enhanced in the MPB region for [Bi_0.5(Na_1-XK_X)_0.5]TiO₃, similar to that observed for Pb(Zr, Ti)O₃.