Influence of tetragonality on crystal orientation induced by a strong magnetic field and on the piezoelectric properties of the (Bi_0.5, Na_0.5)_1−xBa_xTiO₃ ceramic system

抄録

Crystal-oriented (Bi_0.5, Na_0.5)_1−xBa_xTiO₃ (BNBT), (x = 0.1–0.25) ceramics with a perovskite crystal structure were prepared by colloidal processing in a strong rotating magnetic field with the aim of improving their piezoelectric properties. The advantages of increasing the amount of Ba in these ceramics are twofold; specifically, this will lead to anisotropic crystal lattices and it will also increases the tetragonality. The crystal-oriented BNBT (x = 0.1–0.25) ceramics were prepared by using a rotating magnetic field to orient the a- and c-axes of the crystal in the powder compact. The degree of orientation also increased with the tetragonality. The phase transformation that occurred above Curie temperature during sintering redistributed the c-axis-oriented structure along both the a- and c-axes. Again, the c-axis orientation was enhanced by electrical field polarization. The piezoelectric d₃₃ constant, which depended on the Ba content, achieved a maximum value of 122 pC N⁻¹ at a Ba content of 15 mol %.