Morphotropic phase boundary (MPB) plays a key role in tuning piezoelectric responses of ferroelectric ceramics. Here, Bi_0·5Na_0·5TiO₃ modified BiFeO₃–BaTiO₃ ternary solid solutions of 0.7BiFeO₃-(0.3-x)BaTiO₃-xBi_0.5Na_0·5TiO₃ (referred to as BF-BT-xBNT, 0.00 ≤ x ≤ 0.04) were prepared for lead-free piezoelectrics. All the ceramics exhibit an MPB with coexisting rhombohedral (R) and tetragonal (T) phases, and the R/T phase ratio decreases upon increasing x. The increment of BNT promotes the grain growth, lowers the leakage current and Curie temperature (T_C), and gradually drives the ferroelectric to relaxor transition. Because of the MPB with appropriate R/T phase ratio, increased grain size and density, and decreased leakage current, the well-balanced performance between d₃₃ = 206 pC/N and T_C = 488 ℃ is obtained in x = 0.01 case. In addition, the further enhanced in-situ d₃₃ = 286–347 pC/N is obtained in BF-BT-xBNT ceramics along with the improved depolarization temperature T_d from 280 to 312 ℃, showing a potential application for lead-free piezoceramics at high temperature.