Abstract: For (1-x)Na_1/2Bi_1/2TiO₃xBaTiO₃(x=0.02, 0.04, 0.06, 0.08, 0.10) lead-free ceramic system the morphotropic boundary, piezoelectric property, relaxation
property and phase transition were investigated. The piezoelectric ceramics of this system possess large ratios of K_t/K_p and high frequency constants.
According to XRD patterns, the morphotropic boundary lies in the composition range of 0.04<x<0.06. The main physical properties of this system can reach
extreme values near the morphotropic boundary. The relaxation property of this system was studied by using dielectric constant-temperature curves and
thermally stimulated depolarization current (TSDC) curves. Phase transition from ferroelectric to paraelectric phase was also primarily discussed and
it was found out that the ceramics within a composition range possess transitional phase region between ferroelectric phase and paraelectric phase.

Key words: (1-x)Na_1/2Bi_1/2TiO₃-xBaTiO₃, lead-free piezoelectric ceramics, morphotropic boundary, relaxation phase transition, transitional phase region