Anisotropy of ferroelectric behavior of (1-x)Bi1/2Na1/2TiO3-xBaTiO(3) single crystals across the morphotropic phase boundary

Abstract

(1 - x)(Bi1/2Na1/2)TiO3-xBaTiO(3) (BNT-100xBT) single crystals with three different compositions of x = 0.036, 0.065, and 0.088, covering the rhombohedral to predominantly tetragonal region of the phase diagram and encompassing the morphotropic phase boundary (MPB), were grown by top-seeded solution growth. Dielectric and ferroelectric measurements were performed on samples with different orientations with respect to the crystallographic axes. While the results complied with the current understanding of the crystallographic structure, no enhancement of electromechanical properties based on transient polarization rotation was observed. This clearly sets BNT-100xBT apart from other relaxor ferroelectric systems with a rhombohedral-tetragonal MPB such as (1 - x) Pb(Mg1/3Nb2/3)O-3-xPbTiO(3). An anomaly was observed in the poling behavior of the strain in < 001 > oriented BNT-100xBT in the immediate vicinity of the MPB with x = 0.065, resulting in a giant small-signal piezoelectric coefficient d(33) of 4600 pm/V. This effect is hypothesized to be due to an irreversible phase change from rhombohedral polar nanoregions to tetragonal ferroelectric microdomains.