Synthesis, phase segregation and properties of piezo-/ferroelectric (1-x)Pb(Sc_1/2Nb_1/2)O₃-xPbTiO₃ single crystals

Single crystals of the (1-x)Pb(Sc_1/2Nb_1/2)O ₃-xPbTiO₃ [PSN-PT] solid solution are synthesized by the high-temperature solution method using PbO flux with B₂O₃ additive. The grown PSN-PT single crystals contain a Ti concentration lower than the nominal composition (x=0.425-0.51). The effective phase segregation coefficient is found to be k=0.73 for the solid solution. Based on the segregation trend, the PSN-PT crystals of compositions within the morphotropic phase boundary (MPB) region are successfully grown. The MPB crystals show good dielectric and ferroelectric properties with a maximum dielectric constant of 60,000 (at 1 kHz) at T_C=213°C and a remnant polarization of 25 μC/cm² at room temperature. The electromechanical coupling factor k₃₃ of the pre-poled crystals reaches 78%. The T_C and T_MPB of the PSN-PT crystals are much higher than those of the Pb(Mg_1/3Nb_2/3)O₃ (PMN)-PT and Pb(Zn _1/3Nb_2/3)O₃ (PZN)-PT piezocrystals, making them very interesting high-T_C and high-performance piezoelectric materials.