The Rietveld analysis of powder X-ray and neutron diffraction for SBT and Pb_xSr_1-xBi₂Ta₂O₉ revealed that Pb ions were substituted at the perovskite A-site, and the disordering of Pb and Bi ions in Bi₂O₂ layers was not confirmed. The pure solid solutions with the SBT structure were obtained for the samples with x≤0.6, and the unit cell volume slightly increased by Pb substitution. With increasing Pb content (x), parameter c grew while a-b plane was reduced in spite of larger ionic radius of Pb²⁺ than Sr²⁺. These structure changes resulted in a higher T_c for Pb-SBT. Polarization hysteresis measurements using dense ceramics revealed that E_c increased with x while 2P_r at 250kV/cm practically remained constant at around 14μC/cm². The incorporation of Pb into SBT resulted in a higher tilt angle of TaO₆ octahedra along the a-axis (α_x), which is partly responsible for the higher E_c observed for Pb-SBT.