Phase transitional behavior and enhanced electrical properties of Bi(Sc_3/4In_1/4)O₃–PbTiO₃ by small content Pb(Mg_1/3Nb_2/3)O₃ modification

(0.98 − x)Bi(Sc_3/4In_1/4)O₃–xPbTiO₃–0.02Pb(Mg_1/3Nb_2/3)O₃ (BSI–xPT–PMN, x = 0.56–0.60) ternary solid solutions near the morphotropic phase boundary (MPB) have been designed and prepared using the two-step columbite precursor method. Microstructural morphology, phase transition, and electrical properties of the BSI–xPT–PMN ceramics were investigated in detail. X-ray powder diffraction analysis indicated that the BSI–xPT–PMN ceramics were of pure perovskite phase, and the MPB between the rhombohedral and tetragonal phases located at x = 0.58, which are also confirmed by their compositional dependence piezoelectric and electromechanical properties. The piezoelectric properties were enhanced significantly by the introduction of a small amount of PMN, and the piezoelectric constant d ₃₃ is doubled that of the binary Bi(Sc_3/4In_1/4)O₃–PbTiO₃ system. The optimal piezoelectric properties were obtained for the MPB composition 0.40BSI–0.58PT–0.02PMN, which exhibits a piezoelectric constant d ₃₃ of 403 pC/N, planar electromechanical coupling factor k _p of 47.2 %, remnant polarization P _r of 36.4 µC/cm², and Curie temperature T _c of 421 °C. Additionally, the BSI–xPT–PMN systems reduce the content of Sc₂O₃ in comparison with the BS–PT systems. The enhanced piezoelectric performance, together with the good thermal stabilities, makes the BSI–xPT–PMN ceramics promising candidates for high temperature piezoelectric applications.