Dielectric and piezoelectric properties of [0 0 1] and [0 1 1]-poled relaxor ferroelectric PZN-PT and PMN-PT single crystals

Abstract

The properties of PZN-PT and PMN-PT single crystals of varying compositions and orientations have been investigated. Among the various compositions studied, [0 0 1]-optimally poled PZN-(6-7)%PT and PMN-30%PT exhibit superior dielectric and piezoelectric properties, with KT ≈ 6800-8000, d33 ≈ 2800 pC/N, d31 ≈ -(1200-1800) pC/N for PZN-(6-7)%PT; and KT = 7500-9000, d33 = 2200-2500 pC/N and d31 = -(1100-1400) pC/N for PMN-30%PT. These two compositions are also fairly resistant to over-poling. The [0 0 1]-poled electromechanical coupling factors (k33, k31 and kt) are relatively insensitive to crystal composition. [0 1 1]-optimally poled PZN-7%PT single crystal also exhibits extremely high d31 values of up to -4000 pC/N with k31 ≈ 0.90-0.96. While [0 1 1]-poled PZN-7%PT single crystal becomes over-poled with much degraded properties when poled at and above 0.6 kV/mm, PZN-6%PT crystal shows no signs of over-poling even when poled to 2.0 kV/mm. The presence of a certain amount (i.e., 10-15%) of orthorhombic phase in a rhombohedral matrix has been found to be responsible for the superior transverse piezoelectric properties of [0 1 1]-optimally poled PZN-(6-7)%PT. The present work shows that flux-grown PZN-PT crystals exhibit superior and consistent properties and improved over-poling resistance to flux-grown PMN-PT crystals and that, for or a given crystal composition, flux-grown PMN-PT crystals exhibit superior over-poling resistance to their melt-grown counterparts. © 2006 Elsevier B.V. All rights reserved.