Alkaline Earth Substituting Induced MPB Evolution and Property Enhancement in Pb(Mg_1/3Nb_2/3)O₃-PbZrO₃-PbTiO₃:Sm

In this work, based on the lanthanide rare earth Sm³⁺ doped 0.2Pb(Mg_1/3Nb_2/3)O₃-(0.8-x)PbZrO₃-xPbTiO₃:0.015Sm ceramics with a rhombohedral-tetragonal morphotropic phase boundary (MPB) around x = 0.40, we gradually introduced alkaline earth Ba²⁺ and Sr²⁺ at the A-site to substitute Pb²⁺, namely, 0.2A(Mg_1/3Nb_2/3)O₃-0.4AZrO₃-0.4ATiO₃:0.015Sm (A = Pb_0.99-yBa_0.01Sr_y) and conducted a systematic study on their phase structure, domain configuration, and electrical properties. The results indicate that without alkaline earth substituting, the MPB composition shows peak electrical property with piezoelectric coefficient d₃₃ = 477 pC/N and electromechanical coupling factor k_p = 0.59, while an appropriate amount of alkaline earth substituting changes the MPB from rhombohedral-tetragonal coexisting phases to rhombohedral-monoclinic-tetragonal coexisting phases, leading to a significant enhancement in electrical properties with d₃₃ = 687 pC/N and k_p = 0.63 around y = 0.03 for comparison. This work classifies the mechanism for alkaline earth substituting enhanced piezoelectric performance and may provide a guide for the development of high-performance lead-based relaxor ferroelectrics.