Synthesis mechanism of grain-oriented lead-free piezoelectric Na0.5Bi0.5TiO3–BaTiO3 ceramics with giant piezoelectric response

Abstract

In this paper, we report the synthesis of [001]_pc/[012]_Rh (pc: pseudo cubic, Rh: rhombohedral) grain oriented lead-free piezoelectric 0.93(Na_0.5Bi_0.5TiO₃)–0.07BaTiO₃ (NBT–BT) ceramic with Na_0.5Bi_0.5TiO₃ (NBT) as the seed template. The difference in surface energy along with the chemical potential gradient between the stable NBT seeds and the metastable liquid phase was the driving force for the growth of textured grain. Interfaces in the microstructure were found to be coherent at the atomic scale facilitating the domain wall motion with an applied electric field. The strong texturing in [001]_pc/[012]_Rh was found to result in extra structural distortions manifested by a decreasing lattice parameter and increasing rhombohedral angle (α). The textured specimen exhibited rather ordered domains with smaller size as compared to its randomly oriented counterpart. The piezoelectric response was found to increase monotonously with the increase in the degree of texturing and the optimized microstructure was found to provide 200% enhancement in the magnitude of piezoelectric coefficient (d₃₃ ∼ 322 pC N⁻¹) as compared to its randomly oriented form (d₃₃ ∼ 160 pC N⁻¹).