Piezoelectric Properties of (Bi_1/2Na_1/2)TiO₃-Based Solid Solution for Lead-Free High-Power Applications

Abstract

Lead-free piezoelectric ceramics based on x(Bi1/2Na1/2)TiO3–y(Bi1/2Li1/2)TiO3–z(Bi1/2K1/2)TiO3 [x + y + z = 1] (abbreviated as BNLKT100y-100z) were prepared by conventional ceramic fabrication process. In this study, we clarified that the mechanical quality factor Qm of the rhombohedral side of the MPB composition is rather superior to that of the tetragonal side, although the piezoelectric constant d33 of the rhombohedral side is lower than that of the tetragonal side and MPB composition. As a second work, the effects of Mn doping on the variations in Td and piezoelectric properties including high-power characteristics were investigated using BNLKT4-8, which is a rhombohedral composition. The Qm of w wt % MnCO3-doped BNLKT4-8 (abbreviated as BNLKT4-8Mnw) markedly increased with increasing Mn concentration w, while Td, coupling factor k33, and d33 slightly decreased. The high-power characteristics of BNLKT4-8Mn0.6 were superior to those of hard PZT at a vibration velocity v0–p > 0.6 m/s. Therefore, a Mn-doped BNT-based solid solution with rhombohedral symmetry is a promising candidate for lead-free high-power applications.