Tantalum doped 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 piezoelectric ceramics

0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (BNT6BT) ceramics doped with 0–4 mol.% tantalum were investigated in terms of the sintering, microstructure, phase transition, dielectric and piezoelectric properties. Tantalum doping has no remarkable effect on the microstructure and densification within the studied doping content. Up to 4 mol.% tantalum can dissolve into the lattice of BNT6BT ceramics, and the structure symmetry is not changed. However, a significant change in the dielectric behavior and piezoelectric properties took place. With increasing tantalum content, the antiferroelectric phase zone gets broader. Simultaneously, the temperature for a ferroelectric to antiferroelectric phase transition is clearly reduced, and the temperature for a transition from antiferroelectric phases to paraelectric phases is only a bit increased. The results indicate that tantalum occupies B site of a perovskite and behaves as a donor, generating A-site cation vacancies. The properties of the material thus become softer, concerning a reduced coercive field and an improved piezoelectric constant. More than 2 mol.% tantalum doping induces antiferroelectric properties, showing a typical double hysteresis loops, accompanied by a large maximum strain.