Abstract
Much attention is drawn to the preparation, structure and properties investigation of lead-free ferroelectrics for the next generation of piezoelectric devices. (Na0.5Bi0.5)TiO3-BaTiO3 (NBT-BT) lead-free solid solution piezoelectric single crystals with composition x in the range of 0–0.05 as a materials with high piezoelectric properties were successfully grown from platinum crucible by using the top-seeded solution growth (TSSG) method. The dimensions of NBT-BT crystal is Ø40 × 10 mm2. X-ray powder diffraction patterns reveal that the crystal structure of NBT-BT crystal changes from rhombohedral to tetragonal symmetry with increasing amounts of BT(x). The dielectric, ferroelectric and piezoelectric properties of NBT-BT crystals with different compositions near the morphotropic phase boundary (MPB) were studied systematically. Ions (Mn, Eu, Zn) doped NBT and NBT-BT 95/5 crystals were also grown and studied. In addition, their piezoelectric and ferroelectric properties are investigated. Further, a high-quality and large-sized (K0.25Na0.75)NbO3 (KNN25/75) single crystal has been achieved by a carefully controlled TSSG method. The dimensions of the as-grown KNN25/75 single crystal reached up to Ø30 × 10 mm2. The obtained KNN crystals provided us a superb material for the dielectric, piezoelectric, ferroelectric and electromechanical coupling property characterization along different orientations.
Highlights
Relaxor-based ferroelectrics are a hot topic at present, in terms of their practical applications and the mechanism that explains their novel properties [1]
Among all kinds of lead-free piezoelectric systems, sodium bismuth titanate (Na0.5Bi0.5TiO3, abbreviated as NBT) is a strong ferroelectric and the piezoelectric performance can be enhanced by forming solid solutions with barium titanate (BaTiO3, abbreviated as BT) at the composition of hombohedral-tetragonal morphotropic phase boundary (MPB)
When the [001] oriented rhombohedral 0.92NBT-0.08KBT crystal with the engineered-domain configuration is actuated by an electric field along the [001] direction, the four possible polar directions are expected to incline close to the E field direction in each domain, which results in an increased rhombohedral lattice distortion and a high piezoelectric response
Summary
Relaxor-based ferroelectrics are a hot topic at present, in terms of their practical applications and the mechanism that explains their novel properties [1]. The piezoelectric and ferroelectric properties enhanced because the leakage current of NBT-BT crystals decreased notably upon ions substitution [19,20,21,22,23]. As another kind of lead free materials, alkaline niobate (KxNa1−x)NbO3 (KNN)-based solid solutions have been attracting much attention as they are believed to provide a relatively high piezoelectric response, a high Curie temperature and a high acoustic velocity. Properties and Phase Structure of Lead-Free Ferroelectric Single Crystals
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