Phase Structure and Electric Property of BiFeO₃ Doped 0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃ Piezoelectric Ceramics

(1-x)(0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃)-xBiFeO₃ (BNBT6-xBF, 0.02≤x≤0.10, molar fraction) lead-free piezoelectric ceramics were prepared by the conventional solid-state reaction method, and the effects of BiFeO₃ doping content (namely x) on the crystal structure, the dielectric, ferroelectric and electric field induced strain response properties of the ceramics were investigated. The results show that the obtained BNBT6-xBF ceramics all had a pure perovskite structure. The crystal structure of the ceramics was still near the morphotropic phase boundary with x less than 0.08 while changed to pseudo cubic structure with x equal to 0.09. The doping of BiFeO₃ was favorable for the increase of ceramic dielectric constant. With the increase of BiFeO₃ doping content, a phase transition from morphotropic phase to pseudocubic phase was induced in the ceramics and the ferroelectric property decreased. The electric field induced strain first increased then decreased and reached the maximum value of 0.28% with x equal to 0.09, meanwhile the normalized piezoelectric constant was 440 pm ·V^-1.