MnO Modification on Microstructure and Electrical Properties of Lead‐Free Bi _0.485 Na _0.425 K _0.06 Ba _0.03 TiO ₃ Solid Solution Around Morphotropic Phase Boundary

MnO‐added Bi _0.485 Na _0.425 K _0.06 Ba _0.03 TiO ₃ solid solution around the morphotropic phase boundary is produced by the solid oxide reaction process. All the specimens maintain a coexistence of rhombohedral and tetragonal phases, while the suitable addition of MnO apparently promoted grain growth. Besides, the suitable addition of MnO results in the increase of the dielectric permittivity ɛ _r , piezoelectric strain d ₃₃ , electromechanical coupling k _p , and the mechanical quality Q _m , together with a decrease of dissipation factor tan δ. The specimen added with 0.30 wt% MnO reaches an optimal electrical properties: ɛ _r =863, tan δ=0.0124, d ₃₃ =190 pC/N, k _p =0.32, and Q _m =314.