Microstructure, electrical properties of Bi2NiMnO6-doped 0.935(Bi1/2Na1/2) TiO3-0.065BaTiO3 lead-free piezoelectric ceramics

The 0.935Bi1/2Na1/2TiO3-0.065BaTiO3-xmol⋅Bi2NiMnO6(x = 0-0.008) (abbreviated as BNT-BT6.5-xBNMO) lead-free piezoelectric ceramics were fabricated by conventional solid-state reaction method and the effects of BNMO addition on microstructure and electrical properties of the ceramics were investigated. Results show that all samples have formed dense structures with a large relative density > 95%. X-ray diffraction (XRD) patterns show all compositions had a pure perovskite structure, suggesting BNMO effectively diffused into the BNT-BT6.5 lattice to form a solid solution. SEM images indicate that BNMO modified ceramics have a clear grain boundary and a uniformly distributed grain size. The measurements of electrical properties reveal that the electrical properties of BNT-BT-xBNMO ceramics have been greatly improved by certain amount of BNMO substitutions. At room temperature, the BNT-BT-xBNMO ceramics with appropriated BNMO exhibited optimum ferroelectric and piezoelectric properties with a relatively high remnant polarization Pr of 31 μC/cm2, high planar electromechanical coefficient kp of 31% and large piezoelectric constant d33 of 229 pC/N, respectively. These results indicate that the modified BNT-BT6.5 ceramics are promising lead-free piezoelectric candidates for practical applications.