The (1-x)[Na 0.5 Bi 2.5 Ta 2 O 9 ]x[Sr 0.8 Bi 2.15 Ta 2 O 9 ] (0≤x≤1) solid solution ceramics were synthesized using a conventional sintering method. All the ceramic samples consisted of a single phase with an orthorhombic symmetry A2 1 am and showed well-developed polarization-electric field hysteresis loops. The temperature dependence of the dielectric constant revealed that the Curie temperature T c linearly decreased with an increase in x from 780°C(x=0) to 410°C(x=1.0). The maximum electromechanical coupling factor (k p = 8.6 %) and mechanical quality factor (Q m = 7000) with a radial-extensional mode were obtained for the x=0.75 samples.